Rubber composition containing organofunctional silane

ABSTRACT

A rubber composition containing a rubber component, a filler and at least one organofunctional silane and/or mixture of organofunctional silanes in which individual silanes possess both free and blocked mercaptan functionality or particular mixtures of the organofunctional silanes possess both free and blocked mercaptan functionality. The organofunctional silanes and silane mixtures are useful, inter alia, as coupling agents for elastomeric compositions, e.g., rubber formulations employed in the manufacture of tires, where they exhibit a desirable balance of low scorch and good performance properties.

FIELD OF THE INVENTION

The present invention relates to a rubber composition containing arubber component, a filler and at least one organofunctional silaneand/or mixture of organofunctional silanes possessing mercaptan andblocked mercaptan functionality.

DESCRIPTION OF THE RELATED ART

Glycol derivatives of organosilanes are known in the art. However, thesesilane derivatives suffer from a tendency to yield bridged structures infavor of cyclic structures exclusively or primarily, leading to highviscosities and gellation, which limits their usefulness in elastomermanufacture.

Polyether-based monol derivatives of sulfur silanes are also known.Their use suffers from the hazards associated with the use of ethers,which have a tendency to spontaneously form peroxides thus presenting asubstantial flammability risk, as well as the possibility of interferingwith the usefulness of the silanes as coupling agents in elastomers.

Blocked mercaptosilanes, such as thiocarboxylate-functional silanes, aredescribed, e.g., in U.S. Pat. Nos. 6,127,468, 6,414,061 and 6,528,673. Apresentation on the subject of blocked mercaptosilanes was also given atthe 2002 International Tire Exposition and Conference (ITEC) in Akron,Ohio. The blocked mercaptosilanes of these patents possess hydrolyzablegroups which are derived from simple monofunctional alcohols. Whenemployed as coupling agents for rubber compositions used in themanufacture of tires, the thiocarboxalate-functional silanes of U.S.Pat. Nos. 6,127,468, 6,414,061 and 6,528,673 allow tires to bemanufactured with fewer steps. However, during the rubber compoundingoperation, these blocked mercaptosilanes generate volatile organiccompound (VOC) emissions.

This concern regarding VOC emissions, which represents a growingenvironmental problem in the use of silane coupling agents is addressed,by the cyclic diol-derived blocked organofunctional dimeric andoligomeric silanes described in published U.S. Patent Application2005/0245753 and U.S. patent application Ser. No. 11/104,103, filed Apr.12, 2005, and Ser. No. 11/208,367, filed Aug. 19, 2005. Another approachto the issue of VOC emissions is the use of high boiling monofunctionalalcohol-derived silanes as disclosed in U.S. Pat. No. 6,849,754.

In addition to the need to reduce VOC's during the preparation ofinorganic filled elastomers, there is also a need to improve thecoupling efficiency between the inorganic filler and organic polymerwhile maintaining processability of the elastomeric compositions. Bettercoupling improves the performance of cured articles, such as tires, byreducing rolling resistance, heat build-up and wear. U.S. Pat. No.6,635,700 describes the use of a mixture of free and blockedmercaptosilanes to achieve better coupling. However, these mixtures emitVOC's upon use. The level of mercaptosilane in these mixtures is limitedbecause this additive reduces the scorch time of the uncured filledelastomer. In an attempt to lengthen the scorch time of uncured filledelastomers containing mercaptosilanes, published U.S. Patent Application2004/0014840 discloses the use of thiuram disulfide accelerators incombination with functionalized organosilane.

SUMMARY OF THE INVENTION

The present invention is directed to a rubber composition comprising (a)at least one rubber component, (b) at least one particulate filler and(c) at least one organofunctional silane selected from the groupconsisting of:

-   (i) mercaptosilane possessing at least one hydroxyalkoxysilyl group    and/or a cyclic dialkoxysilyl group,-   (ii) blocked mercaptosilane possessing at least one    hydroxyalkoxysilyl group and/or a cyclic dialkoxysilyl group,-   (iii) mercaptosilane dimer in which the silicon atoms of the    mercaptosilane units are bonded to each other through a bridging    dialkoxy group, each silane unit optionally possessing at least one    hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group,-   (iv) blocked mercaptosilane dimer in which the silicon atoms of the    blocked mercaptosilane units are bonded to each other through a    bridging dialkoxy group, each silane unit optionally possessing at    least one hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group,-   (v) silane dimer possessing a mercaptosilane unit the silicon atom    of which is bonded to the silicon atom of a blocked mercaptosilane    unit through a bridging dialkoxy group, each silane unit optionally    possessing at least one hydroxyalkoxysilyl group or a cyclic    dialkoxysilyl group,-   (vi) mercaptosilane oligomer in which the silicon atoms of adjacent    mercaptosilane units are bonded to each other through a bridging    dialkoxy group, the terminal mercaptosilane units possessing at    least one hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group,-   (vii) blocked mercaptosilane oligomer in which the silicon atoms of    adjacent blocked mercaptosilane units are bonded to each other    through a bridging dialkoxy group, the terminal mercaptosilane units    possessing at least one hydroxyalkoxysilyl group or a cyclic    dialkoxysilyl group, and-   (viii) silane oligomer possessing at least one mercaptosilane unit    and at least one blocked mercaptosilane unit, the silicon atoms of    adjacent silane units being bonded to each other through a bridging    dialkoxy group, the terminal silane units possessing at least one    hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group, with the    proviso that,    where the composition contains one or more of (i), (iii) and (vi),    the composition additionally contains one or more of (ii), (iv),    (v), (vii) and (viii), and where the composition contains one or    more of (ii), (iv) and (vii), the composition additionally contains    one or more of (i), (iii), (v), (vi) and (viii).

Organofunctional silanes (i)-(viii) and/or their mixtures, supra, can beprepared by the transesterification of at least one mercaptosilane,blocked mercaptosilane or mixture of mercaptosilane(s) and blockedmercaptosilane(s) with at least one polyhydroxy-containing compound,part or all of the transesterified reaction product(s) thereafter beingoptionally treated, e.g., in a deblocking operation to convert blockedmercaptan functionality if present to free mercaptan functionality or inan esterification operation to convert free mercaptan functionality ifpresent to blocked mercaptan functionality.

As will be appreciated from the foregoing, the rubber composition ofthis invention can include one or more silane dimers and/or oligomers inwhich adjacent silane units are bonded to each other through bridgeddialkoxysilane structures derived from polyhydroxy-containing compounds,e.g., diols (glycols), triols, tetrols, etc., all of which are lowvolatile organic compounds (VOCs) relative to simplemonohydroxy-containing compounds such as methanol and ethanol which arereleased by known mercaptosilanes, blocked mercaptosilanes and/orpolysulfide silanes.

It will also be appreciated that all of the rubber compositions withinthe scope of the invention contain in their organofunctional silane(s)both mercapto- and blocked mercapto-functionalities, either present inthe same silane or in mixtures of individual silanes. While it is knownthat silanes possessing exclusively mercaptan functionality are prone toscorchiness, it has come as a surprise that the compositions of thisinvention which possess both mercaptan and blocked mercaptanfunctionalities possess long scorch times, e.g., approaching those ofsilanes possessing exclusively blocked mercaptan, but with significantlybetter performance than the latter.

DETAILED DESCRIPTION OF THE INVENTION

The expression “organofunctional silane” as used herein shall beunderstood to mean a non-polymeric, dimeric or oligomeric silanepossessing mercaptan and/or blocked mercaptan functionality and at leastone hydroxyalkoxysilyl and/or cyclic dialkoxysilyl group, and, in thecase of the dimeric and oligomeric organofunctional silanes, possessdialkoxy bridging groups linking adjacent silane units.

The expression “rubber composition” as used herein shall be understoodto mean a rubber-forming material or a rubber derived from arubber-forming material.

Organofunctional silanes (i)-(viii) of the present invention and theirmixtures can be obtained, inter alia, from one or more silanes of thegeneral formulae:[[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX₃)_(s)  (1)[(X₃Si)_(q)-G²]_(a)-[Y—[S-G²-SiX₃]_(b)]_(c)  (2)(HS)_(r)-G²-(SiX₃)_(s)  (3)wherein:

each occurrence of Y is independently selected from a polyvalent species(Q)_(z)A(═E), wherein the atom (A) attached to an unsaturated heteroatom(E) is attached to a sulfur, which in turn is linked by means of a groupG² to a silicon atom;

each occurrence of R is independently selected from the group consistingof hydrogen, straight, cyclic or branched alkyl that may or may notcontain unsaturation, alkenyl groups, aryl groups, and aralkyl groups,wherein each R, other than hydrogen, contains from 1 to 18 carbon atoms;

each occurrence of G¹ is independently selected from the groupconsisting of monovalent and polyvalent groups derived by substitutionof alkyl, alkenyl, aryl, or aralkyl wherein G¹ can have from 1 to about30 carbon atoms, with the proviso that if G¹ is univalent, G¹ can behydrogen;

each occurrence of G² is independently selected from the groupconsisting of divalent or polyvalent group derived by substitution ofalkyl, alkenyl, aryl, or aralkyl wherein G² can have from 1 to 30 carbonatoms;

each occurrence of X is independently selected from the group consistingof —Cl, —Br, RO—, RC(═O)O—, R₂C═NO—, R₂NO—, R₂N—, —R, wherein each R isas above;

each occurrence of Q is independently selected from the group consistingof oxygen, sulfur, and (—NR—);

each occurrence of A is independently selected from the group consistingof carbon, sulfur, phosphorus, and sulfonyl;

each occurrence of E is independently selected from the group consistingof oxygen, sulfur, and (—NR—);

each occurrence of the subscripts, a, b, c, j, k, p, q, r, s, and z areindependently given by a is 0 to about 7; b is 1 to about 3; c is 1 toabout 6; j is 0 to about 1, but j may be 0 only if p is 1; k is 1 to 2,with the provisos that

if A is carbon, sulfur, or sulfonyl, then (i) a+b=2 and (ii) k=1;

if A is phosphorus, then a+b=3 unless both (i) c>1 and (ii) b=1, inwhich case a=c+1; and if A is phosphorus, then k is 2; p is 0 to 5, q is0 to 6; r is 1 to 3; s is 1 to 3; z is 0 to about 3 and with the provisothat each of the above structures contains at least one hydrolysable Xgroup.

In one particular embodiment of the invention, the silane reactants aretrialkoxysilanes represented by at least one of the general formula:(RO)₃SiG²SC(═O)G¹  (4)(RO)₃SiG²SH  (5)wherein each R independently has one of the aforestated meanings and,advantageously, is a methyl, ethyl, propyl, isopropyl, n-butyl, orsec-butyl group; G² is an alkylene group of from 1 to about 12 carbonatoms; and, G¹ is an alkyl group of from 3 to about 12 carbon atoms.

Mixtures of different silane monomers (1, 2 and/or 3) can be used, e.g.,two or more mercaptotrialkoxysilanes of Formula (5), two or morethiocarboxylate trialkoxysilanes of Formula (4) and mixtures of one ormore mercaptotrialkoxysilanes (5) and one or more thiocarboxylatetrialkoxysilanes (4) with R, G¹ and G² in these silanes being defined asin silanes (1) and (3).

In a silane dimer or oligomer of this invention, each silane unit of thedimer or oligomer is bonded to an adjacent silane unit through abridging group resulting from the reaction of the selected silanemonomer(s) with one or more polyhydroxy-containing compounds of thegeneral formula:G³(OH)_(d)  (6)wherein G³ is a hydrocarbon group of from 1 to about 15 carbon atoms ora heterocarbon group of from 4 to about 15 carbon atoms containing oneor more etheric oxygen atoms and d is an integer of from 2 to about 8.

In one embodiment of the invention, polyhydroxy-containing compound (6)is a diol (glycol) of at least one of the general formulae:HO(R⁰CR⁰)_(f)OH  (7)HO(CR⁰ ₂CR⁰ ₂O)_(e)H  (8)wherein R⁰ is independently given by one of the members listed above forR, f is 2 to about 15 and e is 2 to about 7. Representative examples ofsuch diols are HOCH₂CH₂OH, HOCH₂CH₂CH₂OH, HOCH₂CH₂CH₂CH₂OH,HOCH₂CH(CH₃)CH₂OH, etc., a diol possessing an etheric oxygen-containinggroup such as HOCH₂CH₂OCH₂CH₂OH, HOCH₂CH₂OCH₂CH₂OCH₂CH₂OH,HOCH₂CH₂CH₂OCH₂ CH₂CH₂OH, and a diol possessing a polyether backbonesuch as a diol of Formula (8) in which R⁰ is hydrogen or methyl and e is3 to about 7

In another embodiment of the invention, polyhydroxy-containing compound(5) possesses higher hydroxyl functionality, e.g., a triol or tetrol, ofthe general formula:G³(OH)_(d)  (9)wherein G³ is a substituted hydrocarbon group from 2 to about 15 carbonatoms or a substituted heterocarbon from 4 to about 15 carbon atoms andcontains one or more etheric oxygen atoms; and d is an integer of from 3to about 8. Examples of higher hydroxyl functionality compounds (9)include glycerol, trimethylolethane, trimethylolpropane,1,2,4-butanetriol, 1,2,6-hexanetriol, pentaerythritol,dipentaerythritol, tripentaerythritol, mannitol, galacticol, sorbitol,etc.

Mixtures of polyhydroxy-containing compounds (6) can also be usedherein.

Organofunctional silanes (i)-(viii) and mixtures thereof can be preparedby the process which comprises reacting at least one silane of one ormore of general formulae (1), (2), and/or (3) supra:[[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX₃)_(s)  (1)[(X₃Si)_(q)-G²]_(a)-[Y—[S-G²-SiX₃]_(b)]_(c)  (2)(HS)_(r)-G²-(SiX₃)_(s)  (3)with at least one polyhydroxy-containing compound of the general formula(6):G³(OH)_(d)  (6)wherein each occurrence of G¹, G², G³, R, Y, X, a, b, c, d, j, k, p, r,and s are defined supra and with the proviso that at least one of the Xis a hydrolyzable group, each of the aforesaid having the meaningspreviously stated, under transesterification reaction conditions, partor all of the product(s) of the reaction being optionally treated toconvert blocked mercaptan functionality, if present, to mercaptanfunctionality, or to convert mercaptan functionality, if present, toblocked mercaptan functionality.

In a first embodiment of the foregoing process at least one blockedmercaptosilane (1) or (2) is transesterified with at least onepolyhydroxy-containing compound (6), optionally, in the presence ofcatalyst, e.g., transesterification catalyst, to provide one or moreorganofunctional blocked mercaptosilanes (ii), (iv) and (vii), part orall of the blocked mercaptosilane(s) thereafter being subjected topartial or complete deblocking to provide one or more organofunctionalsilanes (i), (iii), (iv), (vi) and (viii), any of which may be inadmixture with one or more of (ii), (iv), and (vii) depending on theextent of deblocking.

In one application of this first embodiment of the general preparativeprocess herein, at least one thiocarboxylate trialkoxysilane (4) istransesterified with at least one diol (7) or (8), optionally, in thepresence of a transesterification catalyst such as para-toluenesulfonicacid, to provide organofunctional silane (vii), i.e., blockedmercaptosilane oligomer, which can thereafter be subjected to partialdeblocking employing a suitable base such as alkali metal alkoxide,e.g., sodium ethoxide in ethanol, to yield one or more organofunctionalsilanes (viii), i.e., silane oligomer containing one or moremercaptosilanes and one or more blocked mercaptosilanes, alone or incombination with one or more other organofunctional silanes (i)-(vi).

In a second embodiment of the general preparative procedure herein, atleast one mercaptosilane (3) in admixture with at least one blockedmercaptosilane (1) or (2) are transesterified with at least onepolyhydroxy-containing compound (6), optionally, in the presencetransesterification catalyst, to provide, inter alia, one or moreorganofunctional silanes (v) and/or (viii), and/or other mixtures oforganofunctional silanes, e.g., a mixture of silanes (i) and (ii), (i)and (v), (i), (ii) and (v), (i), (ii) and (v), (ii) and (viii), (ii),(v) and (viii), (i), (ii), (v) and (viii), etc.

In one application of the foregoing second embodiment of the generalpreparative process, at least one mercaptotrialkoxysilane (5) and atleast one thiocarboxylate trialkoxysilane (4) are transesterifiedtogether with at least one diol (7), optionally, in the presence oftransesterification catalyst, to provide one or more silanes (v) and/or(viii) which, if desired, can be subjected to deblocking to increase theamounts of mercaptosilane relative to blocked mercaptosilane in aparticular silane product or mixture of silane products.

In a third embodiment of the general preparative process, at least onemercaptosilane (3) is transesterified with at least onepolyhydroxy-containing compound (6), optionally, in the presence oftransesterification catalyst, to provide at least one dimer (iii) and/oroligomer (vi), or mercaptosilane (i) alone or in admixture with dimer(iii) and/or oligomer (iv). Optionally, any of these transesterificationproducts or their mixtures can be subjected to esterification with acarboxylic acid or acid halide to block mercapto groups therein.

In one application of the foregoing third embodiment of the generalpreparative process, at least one mercaptotrialkoxysilane (5) istransesterified with at least one diol (7), optionally, in the presenceof transesterification catalyst, to provide mercaptosilane dimer (iii)and/or oligomer (vi).

It is also within the scope of the invention to combine part or all ofthe esterification product(s) obtained from one of the aforedescribedprocess embodiments with part or all of the product(s) obtained from oneof the other process embodiments. Thus, e.g., blocked mercaptosilanedimer (iv) and/or blocked mercaptosilane oligomer (vii) resulting fromthe first preparative procedure can be admixed with mercaptosilane dimer(iii) and/or mercaptosilane oligomer (vi) to provide a mixture oforganofunctional silanes possessing both mercaptan and blocked mercaptanfunctionalities. In a similar manner, simple mixing of the esterifiedproduct(s) of one particular embodiment of the general preparativeprocess can be admixed with the esterified product(s) of anotherembodiment of the general preparative process to provide still othercompositions within the scope of the invention possessing both mercaptanand blocked mercaptan functionality.

Reaction conditions for the process of preparing organofunctionalsilanes (i)-(viii) and their mixtures include molar ratios of silane(s),determined by adding the individual molar contribution of silanes (1),(2) and (3), and polyhydroxy-containing compound(s) (6) of from about0.1 to about 3 moles of (6) per mole of silyl group, determined byadding the individual contribution of silanes (1), (2) and (3), atemperature of from about 0° C. to about 150° C., a pressure of fromabout 0.1 to about 2,000 mmHg, and in the optional presence of catalyst,solvent, etc.

In a specific embodiment of the present invention, the rubbercomposition contains at least one organofunctional silane selected fromthe group consisting of:[[[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX_(u)Z^(b) _(v)Z^(c)_(w))_(s)]_(m)[(HS)_(r)-G²-(SiX_(u)Z^(b) _(v)Z^(c) _(w))_(s)]_(n)  (10)and[[(X_(v)Z^(b) _(v)Z^(c) _(w)Si)_(q)-G²]_(a)-[Y—[S-G²-SiX_(u)Z^(b)_(v)Z^(c) _(w)]_(b)]_(c)]_(m)[(HS)_(r)-G²-(SiX_(u)Z^(b) _(v)Z^(c)_(w))_(s)]_(n)  (11)wherein:

each occurrence of Y is independently selected from a polyvalent species(Q)_(z)A(=E), wherein the atom (A) attached to an unsaturated heteroatom(E) is attached to a sulfur, which in turn is linked by means of a groupG² to a silicon atom;

each occurrence of R is independently selected from the group consistingof hydrogen, straight, cyclic or branched alkyl that may or may notcontain unsaturation, alkenyl groups, aryl groups, and aralkyl groups,wherein each R, other than hydrogen, contains from 1 to 18 carbon atoms;

each occurrence of G¹ is independently selected from the groupconsisting of monovalent and polyvalent groups derived by substitutionof alkyl, alkenyl, aryl, or aralkyl wherein G¹ can have from 1 to about30 carbon atoms, with the proviso that if G¹ is univalent, G¹ can behydrogen;

each occurrence of G² is independently selected from the groupconsisting of divalent or polyvalent group derived by substitution ofalkyl, alkenyl, aryl, or aralkyl wherein G² can have from 1 to 30 carbonatoms;

each occurrence of X is independently selected from the group consistingof —Cl, —Br, RO—, RC(═O)O—, R₂C═NO—, R₂NO—, R₂N—, —R, HO(R⁰CR⁰)_(f)O—,wherein each R is as above and each occurrence of R⁰ is independentlygiven by one of the members listed above for R;

each occurrence of Z^(b), which forms a bridging structure between twosilicon atoms, is independently selected from the group consisting of(—O—)_(0.5), and [—O(R⁰CR⁰)_(f)O—]_(0.5), wherein each occurrence of R⁰is independently given by one of the members listed above for R;

each occurrence of Z^(c), which forms a cyclic structure with a siliconatom, is independently given by —O(R⁰CR⁰)_(f)O— wherein each occurrenceof R⁰ is independently given by one of the members listed above for R;

each occurrence of Q is independently selected from the group consistingof oxygen, sulfur, and (—NR—);

each occurrence of A is independently selected from the group consistingof carbon, sulfur, phosphorus, and sulfonyl;

each occurrence of E is independently selected from the group consistingof oxygen, sulfur, and (—NR—);

each occurrence of the subscripts, a, b, c, f, j, k, m, n, p, q, r, s,u, v, w, and z is independently given by a is 0 to about 7; b is 1 toabout 3; c is 1 to about 6; f is about 2 to about 15, j is 0 to about 1,but j may be 0 only if p is 1; k is 1 to 2, with the provisos that

if A is carbon, sulfur, or sulfonyl, then (i) a+b=2 and (ii) k=1;

if A is phosphorus, then a+b=3 unless both (i) c>1 and (ii) b=1, inwhich case a=c+1; and if A is phosphorus, then k is 2; m is 1 to about20, n is 1 to about 20, p is 0 to 5, q is 0 to 6; r is 1 to 3; s is 1 to3; u is 0 to 3; v is 0 to 3; w is 0 to 1 with the proviso that u+v+2w=3;z is 0 to about 3; and with the proviso that the each of the abovestructures contains at least one hydrolysable group, Z^(b) or Z^(c),that is a difunctional alkoxy group.

In accordance with another embodiment of the present invention, aprocess for the preparation of an organofunctional silane containingcyclic hydroxyalkyloxysilyl groups, and/or bridging dialkoxysilyl groupsand both free and blocked mercaptan functionality groups is providedwhich comprises blending at least one blocked mercaptofunctional silaneof the formula:[[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX₃)_(s)  (1)and/or of the formula:[(X₃Si)_(q)-G²]_(a)-[Y—[S-G²-SiX₃]_(b)]_(c)  (2)with at least one mercaptofunctional silane of the formula:(HS)_(r)-G²-(SiX₃)_(s)  (3)wherein each occurrence of G¹, G², R, Y, X, a, b, c, j, k, p, q, r, ands have one of the aforestated meanings and with the proviso that atleast one of X is a hydrolyzable group, and transesterifying the mixturewith a diol HO(R⁰CR⁰)_(f)OH, advantageously in the presence of atransesterification catalyst wherein R⁰ and f have one of theaforestated meanings.

In still another embodiment of the invention, a process for thepreparation of an organofunctional silane containing cyclic and/orbridging dialkoxy silyl groups and both free and blocked mercaptanfunctionality is provided which comprises reacting a cyclic and/orbridging dialkoxysilane with a metal alkoxide.

As used herein in connection with silanes (10) and (11), the terms“diol” and “difunctional alcohol” refer to any structure of the generalFormula (7):HO(R⁰CR⁰)_(f)OH  (7)wherein f and R⁰ are as defined above. These structures representhydrocarbons in which two hydrogen atoms are replaced with —OH inaccordance with compounds (7), supra.

As used herein in connection with silanes (10) and (11), “dialkoxy” and“difunctional alkoxy” refer to hydrocarbon-based diols in which the twoOH hydrogen atoms have been removed to give divalent radicals, and whosestructures are represented by the general formula:—O(R⁰CR⁰)_(f)O—  (12)wherein f and R⁰ are as defined above.

As used herein in connection with silanes (10) and (11), “cyclicdialkoxy” refers to a silane or group in which cyclization is about asilicon atom by two oxygen atoms each of which is attached to a commondivalent hydrocarbon group such as is commonly the case with diols.Cyclic dialkoxy groups herein are represented by Z^(c). The structure ofZ^(c) is important in the formation of the cyclic structure. R⁰ groupsthat are more sterically hindered than hydrogen promote the formation ofcyclic structures. The formation of cyclic structures is also promotedwhen the value of f in diol (7) is 2 or 3, and more preferrably 3.

As used herein in connection with silanes (10) and (11), “bridgingdialkoxy” refers to a silane or group in which two different siliconatoms are each bound to one oxygen atom, which in turn is bound to acommon divalent hydrocarbon group such as is commonly found in diols.Bridging dialkoxy groups herein are represented by Z^(b).

As used herein in connection with silanes (10) and (11), “hydroxyalkoxy”refers to a silane or group in which one OH hydrogen atom has beenremoved to provide a monovalent radical, and whose structures arerepresented by the general formula:HO(R⁰CR⁰)_(f)O—  (13)wherein f and R⁰ are defined above. Hydroxyalkoxy groups herein arerepresented by X.

As used herein in connection with silanes (10) and (11), the term“hydrocarbon based diols” refers to diols that contain two OH groups aspart of a hydrocarbon structure. Absent from these hydrocarbon baseddiols are heteroatoms (other than, of course, the oxygens in the OHgroups), in particular ether groups, which are deliberately avoided dueto problems associated with their tendency to spontaneously formperoxides which may lead to flammability hazards and free radicalformation.

The structure (7) will be referred to herein as the appropriate diol (ina few specific cases, glycol is the more commonly used term), prefixedby the particular hydrocarbon group associated with the two OH groups.Examples include neopentylglycol, 1,3-butanediol, and2-methyl-2,4-pentanediol.

The structure (12) will be referred to herein as the appropriatedialkoxy, prefixed by the particular hydrocarbon group associated withthe two OH groups. Thus, for example, the diols, neopentylglycol,1,3-butanediol, and 2-methyl-2,4-pentanediol correspond herein to thedialkoxy groups, neopentylglycoxy, 1,3-butanedialkoxy, and2-methyl-2,4-pentanedialkoxy, respectively.

The silanes herein that contain both a free and blockedmercaptofunctional group, in which the diol from which such silanes arederived is commonly referred to as a glycol, are named as thecorresponding glycoxysilane. Cyclic dialkoxy silanes herein, in whichthe diol from which the silane is derived is commonly referred to as adiol, are named as the corresponding dialkoxysilane.

As used herein for Z^(b), the notations, (—O—)_(0.5) and[—O(R⁰CR⁰)_(f)O—]_(0.5), refer to one-half of a siloxane bond, andone-half of a bridging dialkoxy group, respectively. These notations areused in conjunction with a silicon atom and they are taken herein tomean one-half of an oxygen atom, namely, the half bound to theparticular silicon atom, or to one-half of a dialkoxy group, namely, thehalf bound to the particular silicon atom, respectively. It isunderstood that the other half of the oxygen atom or dialkoxy group andits bond to silicon occurs somewhere else in the overall molecularstructure being described. Thus, the (—O—)_(0.5) siloxane groups and the[—O(R⁰CR⁰)_(f)O—]_(0.5) dialkoxy groups mediate the chemical bonds thathold two separate silicon atoms together, whether these two siliconatoms occur intermolecularly or intramolecularly. In the case of[—O(R⁰CR⁰)_(f)O—]_(0.5), if the hydrocarbon group (R⁰CR⁰)_(f) isunsymmetrical, either end of [—O(R⁰CR⁰)_(f)O—]_(0.5) may be bound toeither of the two silicon atoms required to complete the structures ofsilanes (10) and (11).

As used herein in connection with silanes (1), (2), (3), (10) and (11),“alkyl” includes straight, branched and cyclic alkyl groups; “alkenyl”includes any straight, branched, or cyclic alkenyl group containing oneor more carbon-carbon double bond, where the point of substitution canbe either at a carbon-carbon double bond or elsewhere in the group; and“alkynyl” includes any straight, branched, or cyclic alkynyl groupcontaining one or more carbon-carbon triple bonds and, optionally, oneor more carbon-carbon double bonds as well, where the point ofsubstitution can be either at a carbon-carbon triple bond, acarbon-carbon double bond, or elsewhere in the group. Specific examplesof alkyls include, but are not limited to, methyl, ethyl, propyl andisobutyl. Specific examples of alkenyls include, but are not limited to,vinyl, propenyl, allyl, methallyl, ethylidenyl norbornane, ethylidenenorbornyl, ethylidenyl norbornene and ethylidene norbornenyl. Specificexamples of alkynyls include, but are not limited to, acetylenyl,propargyl and methylacetylenyl.

As used herein in connection with silanes (1), (2), (3), (10)) and (11),“aryl” includes any aromatic hydrocarbon from which one hydrogen atomhas been removed; “aralkyl” includes, but is not limited to, any of theaforementioned alkyl groups in which one or more hydrogen atoms havebeen substituted by the same number of like and/or different aryl (asdefined herein) substitutents; and “arenyl” includes any of theaforementioned aryl groups in which one or more hydrogen atoms have beensubstituted by the same number of like and/or different alkyl (asdefined herein) substitutents. Specific examples of aryls include, butare not limited to, phenyl and naphthalenyl. Specific examples ofaralkyls include, but are not limited to, benzyl and phenethyl. Specificexamples of arenyls include, but are not limited to, tolyl and xylyl.

As used herein in connection with silanes (1), (2), (3), (10) and (11),“cyclic alkyl”, “cyclic alkenyl”, and “cyclic alkynyl” also includebicyclic, tricyclic, and higher cyclic structures, as well as theaforementioned cyclic structures further substituted with alkyl,alkenyl, and/or alkynyl groups. Representative examples include, but arenot limited to, norbornyl, norbornenyl, ethylnorbornyl,ethylnorbornenyl, ethylcyclohexyl, ethylcyclohexenyl,cyclohexylcyclohexyl and cyclododecatrienyl.

Representative examples of the functional groups (—YS—) present in thesilanes of the present invention include, but are not limited to,thiocarboxylate ester, —C(═O)—S— (any silane with this functional groupis a “thiocarboxylate ester silane”); dithiocarboxylate, —C(═S)—S— (anysilane with this functional group is a “dithiocarboxylate estersilane”); thiocarbonate ester, —O—C(═O)—S— (any silane with thisfunctional group is a “thiocarbonate ester silane”); dithiocarbonateester, —S—C(═O)—S— and —O—C(═S)—S— (any silane with this functionalgroup is a “dithiocarbonate ester silane”); trithiocarbonate ester,—S—C(═S)—S— (any silane with this functional group is a“trithiocarbonate ester silane”); dithiocarbamate ester, N—C(═S)—S— (anysilane with this functional group is a “dithiocarbamate ester silane”);thiosulfonate ester, —S(═O)₂—S— (any silane with this functional groupis a “thiosulfonate ester silane”); thiosulfate ester, —O—S(═O)₂—S— (anysilane with this functional group is a “thiosulfate ester silane”);thiosulfamate ester, (—N—)S(═O)₂—S— (any silane with this functionalgroup is a “thiosulfamate ester silane”); thiosulfinate ester,C—S(═O)—S— (any silane with this functional group is a “thiosulfinateester silane”); thiosulfite ester, —O—S(═O)—S— (any silane with thisfunctional group is a “thiosulfite ester silane”); thiosulfimate ester,N—S(═O)—S— (any silane with this functional group is a “thiosulfimateester silane”); thiophosphate ester, P(═O)(O—)₂(S—) (any silane withthis functional group is a “thiophosphate ester silane”);dithiophosphate ester, P(═O)(O—)(S—)₂ or P(═S)(O—)₂(S—) (any silane withthis functional group is a “dithiophosphate ester silane”);trithiophosphate ester, P(═O)(S—)₃ or P(═S)(O—)(S—)₂ (any silane withthis functional group is a “trithiophosphate ester silane”);tetrathiophosphate ester P(═S)(S—)₃ (any silane with this functionalgroup is a “tetrathiophosphate ester silane”); thiophosphamate ester,—P(═O)(—N—)(S—) (any silane with this functional group is a“thiophosphamate ester silane”); dithiophosphamate ester,—P(═S)(—N—)(S—) (any silane with this functional group is a“dithiophosphamate ester silane”); thiophosphoramidate ester,(—N—)P(═O)(O—)(S—) (any silane with this functional group is a“thiophosphoramidate ester silane”); dithiophosphoramidate ester,(—N—)P(═O)(S—)₂ or (—N—)P(═S)(O—)(S—) (any silane with this functionalgroup is a “dithiophosphoramidate ester silane”); andtrithiophosphoramidate ester, silane”).

In another embodiment, each occurrence of Y is selected independentlyfrom the group consisting of —C(═NR)—; —SC(═NR)—; —SC(═O)—; (—NR)C(═O)—;(—NR)C(═S)—; —OC(═O)—; —OC(═S)—; —C(═O)—; —SC(═S)—; —C(═S)—; —S(═O)—;—S(═O)₂—; —OS(═O)₂—; (—NR)S(═O)₂—; —SS(═O)—; —OS(═O)—; (—NR)S(═O)—;—SS(═O)₂—; (—S)₂P(═O)—; —(—S)P(═O)—; —P(═O)(−)₂; (—S)₂P(═S)—;—(—S)P(═S)—; —P(═S)(−)₂; (—NR)₂P(═O)—; (—NR)(—S)P(═O)—; (—O)(—NR)P(═O)—;(—O)(—S)P(═O)—; (—O)₂P(═O)—; —(—O)P(═O)—; —(—NR)P(═O)—; (—NR)₂P(═S)—;(—NR)(—S)P(═S)—; (—O)(—NR)P(═S)—; (—O)(—S)P(═S)—; (—O)₂P(═S)—;—(—O)P(═S)—; and, —(—NR)P(═S)—.

In still another embodiment, Y is —C(═O)—.

In another embodiment of the present invention, the novel silane is onein which Y is —C(═O)—, G¹ has a primary carbon atom attached to thecarbonyl and is a C₁-C₁₈ alkyl, and G² is a divalent or polyvalent groupderived by substitution of C₁-C₁₂ alkyl.

In still another embodiment of the present invention, the novel silaneis one in which Y is —C(═O)—, G¹ is a monovalent straight chain groupderived from a C₃-C₁₀, alkyl, and G² is a divalent or polyvalent groupderived by substitution of a C₃-C₁₀ alkyl, p is 0, j is 1 and k is 1 andthe ratio of m to n is in the range of about 20:1 to 3:1.

In yet another embodiment of the present invention, the novel silane isone in which Y is —C(═O)—, G¹ is a monovalent straight chain groupderived from a C₆-C₈ alkyl, G² is a divalent or polyvalent group derivedby substitution of a C₃-C₆ alkyl, p is 0, j is 1 and k is 1 and theratio of m to n is in the range of about 10:1 to about 4:1.

Representative examples of G¹ include, but are not limited to,CH₃(CH₂)_(g)—, wherein g is 1 to about 29; benzyl; 2-phenylethyl;diethylene cyclohexane; 1,2,4-triethylene cyclohexane; diethylenebenzene; phenylene; —(CH₂)_(g)— wherein g is preferably 1 to 29, whichrepresent the terminal straight-chain alkyls further substitutedterminally at the other end, such as —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, and—CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, and their beta-substituted analogs, such as—CH₂(CH₂)_(i)CH(CH₃)—, where i is preferably 0 to 16;—CH₂CH₂C(CH₃)₂CH₂—; the structure derivable from methallyl chloride,—CH₂CH(CH₃)CH₂—; any of the structures derivable from divinylbenzene,such as —CH₂CH₂(C₆H₄)CH₂CH₂— and —CH₂CH₂(C₆H₄)CH(CH₃)—, where thenotation C₆H₄ denotes a disubstituted benzene ring; any of thestructures derivable from dipropenylbenzene, such as—CH₂CH(CH₃)(C₆H₄)CH(CH₃)CH₂—, where the notation C₆H₄ denotes adisubstituted benzene ring; any of the structures derivable frombutadiene, such as —CH₂CH₂CH₂CH₂—, —CH₂CH₂CH(CH₃)—, and —CH₂CH(CH₂CH₃)—;any of the structures derivable from piperylene, such as—CH₂CH₂CH₂CH(CH₃)—, —CH₂CH₂CH(CH₂CH₃)—, and —CH₂CH(CH₂CH₂CH₃)—; any ofthe structures derivable from isoprene, such as —CH₂CH(CH₃)CH₂CH₂—,—CH₂CH(CH₃)CH(CH₃)—, —CH₂C(CH₃)(CH₂CH₃)—, —CH₂CH₂CH(CH₃)CH₂—,—CH₂CH₂C(CH₃)₂— and —CH₂CH[CH(CH₃)₂]—; any of the isomers of—CH₂CH₂-norbornyl-, —CH₂CH₂-cyclohexyl-; any of the diradicalsobtainable from norbornane, cyclohexane, cyclopentane,tetrahydrodicyclopentadiene, or cyclododecene by loss of two hydrogenatoms; the structures derivable from limonene, —CH₂CH(4-CH₃-1-C₆H₉—)CH₃,where the notation C₆H₉ denotes isomers of the trisubstitutedcyclohexane ring lacking substitution in the 2 position; any of themonovinyl-containing structures derivable from trivinylcyclohexane, suchas —CH₂CH₂(vinylC₆H₉)CH₂CH₂— and —CH₂CH₂(vinylC₆H₉)CH(CH₃)—, where thenotation C₆H₉ denotes any isomer of the trisubstituted cyclohexane ring;any of the monounsaturated structures derivable from myrcene containinga trisubstituted C═C, such as —CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH₂CH₂—,—CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH(CH₃)—, —CH₂C[CH₂CH₂CH═C(CH₃)₂](CH₂CH₃)—,—CH₂CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH₂—, —CH₂CH₂(C—)(CH₃)[CH₂CH₂CH═C(CH₃)₂], and—CH₂CH[CH(CH₃)[CH₂CH₂CH═C(CH₃)₂]]—; and, any of the monounsaturatedstructures derivable from myrcene lacking a trisubstituted C═C, such as—CH₂CH(CH═CH₂)CH₂CH₂CH₂C(CH₃)₂—, —CH₂CH(CH═CH₂)CH₂CH₂CH[CH(CH₃)₂]—,—CH₂C(═CH—CH₃)CH₂CH₂CH₂C(CH₃)₂—, —CH₂C(═CH—CH₃)CH₂CH₂CH[CH(CH₃)₂]—,—CH₂CH₂C(═CH₂)CH₂CH₂CH₂C(CH₃)₂—, —CH₂CH₂C(═CH₂)CH₂CH₂CH[CH(CH₃)₂]—,—CH₂CH═C(CH₃)₂CH₂CH₂CH₂C(CH₃)₂—, and —CH₂CH═C(CH₃)₂CH₂CH₂CH[CH(CH₃)₂].

Representative examples of G² include, but are not limited to,diethylene cyclohexane; 1,2,4-triethylene cyclohexane; diethylenebenzene; phenylene; —(CH₂)_(g)— wherein g is preferably 1 to 29, whichrepresent terminal straight-chain alkyls further substituted terminallyat the other end, such as —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, and—CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, and their beta-substituted analogs, such as—CH₂(CH₂)_(i)CH(CH₃)—, where i is preferably 0 to 16;—CH₂CH₂C(CH₃)₂CH₂—; the structure derivable from methallyl chloride,—CH₂CH(CH₃)CH₂—; any of the structures derivable from divinylbenzene,such as —CH₂CH₂(C₆H₄)CH₂CH₂— and —CH₂CH₂(C₆H₄)CH(CH₃)—, where thenotation C₆H₄ denotes a disubstituted benzene ring; any of thestructures derivable from dipropenylbenzene, such as—CH₂CH(CH₃)(C₆H₄)CH(CH₃)CH₂—, where the notation C₆H₄ denotes adisubstituted benzene ring; any of the structures derivable frombutadiene, such as —CH₂CH₂CH₂CH₂—, —CH₂CH₂CH(CH₃)—, and —CH₂CH(CH₂CH₃)—;any of the structures derivable from piperylene, such as—CH₂CH₂CH₂CH(CH₃)—, —CH₂CH₂CH(CH₂CH₃)—, and —CH₂CH(CH₂CH₂CH₃)—; any ofthe structures derivable from isoprene, such as —CH₂CH(CH₃)CH₂CH₂—,—CH₂CH(CH₃)CH(CH₃)—, —CH₂C(CH₃)(CH₂CH₃)—, —CH₂CH₂CH(CH₃)CH₂—,—CH₂CH₂C(CH₃)₂— and —CH₂CH[CH(CH₃)₂]—; any of the isomers of—CH₂CH₂-norbornyl-, —CH₂CH₂-cyclohexyl-; any of the diradicalsobtainable from norbornane, cyclohexane, cyclopentane,tetrahydrodicyclopentadiene, or cyclododecene by loss of two hydrogenatoms; the structures derivable from limonene, —CH₂CH(4—CH₃—1—C₆H₉—)CH₃,where the notation C₆H₉ denotes isomers of the trisubstitutedcyclohexane ring lacking substitution in the 2 position; any of themonovinyl-containing structures derivable from trivinylcyclohexane, suchas —CH₂CH₂(vinylC₆H₉)CH₂CH₂— and —CH₂CH₂(vinylC₆H₉)CH(CH₃)—, where thenotation C₆H₉ denotes any isomer of the trisubstituted cyclohexane ring;any of the monounsaturated structures derivable from myrcene containinga trisubstituted C═C, such as —CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH₂CH₂—,—CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH(CH₃)—, —CH₂C[CH₂CH₂CH═C(CH₃)₂](CH₂CH₃)—,—CH₂CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH₂—, —CH₂CH₂(C—)(CH₃)[CH₂CH₂CH═C(CH₃)₂], and—CH₂CH[CH(CH₃)[CH₂CH₂CH═C(CH₃)₂]]—; and any of the monounsaturatedstructures derivable from myrcene lacking a trisubstituted C═C, such as—CH₂CH(CH═CH₂)CH₂CH₂CH₂C(CH₃)₂—, —CH₂CH(CH═CH₂)CH₂CH₂CH[CH(CH₃)₂]—,—CH₂C(═CH—CH₃)CH₂CH₂CH₂C(CH₃)₂—, —CH₂C(═CH—CH₃)CH₂CH₂CH[CH(CH₃)₂]—,—CH₂CH₂C(═CH₂)CH₂CH₂CH₂C(CH₃)₂—, —CH₂CH₂C(═CH₂)CH₂CH₂CH[CH(CH₃)₂]—,—CH₂CH═C(CH₃)₂CH₂CH₂CH₂C(CH₃)₂— and —CH₂CH═C(CH₃)₂CH₂CH₂CH[CH(CH₃)₂].

In another embodiment of the present invention, the silane (10) has astructure in which the sum of the carbon atoms in its G¹ and G² groupsis from 3 to 18 and, advantageously, is from 6 to 14. The amount ofcarbon in the blocked mercapto fragment facilitates the dispersion ofthe inorganic filler into the organic polymers, thereby improving thebalance of properties in the cured filled rubber.

In yet another embodiment of the present invention, G¹ is—CH₃CH₂CH₂CH₂CH₂CH₂CH₂— and G² is —CH₂CH₂CH₂—, r is 1 and s is 1.

Representative examples of R and R⁰ groups are hydrogen, branched andstraight-chain alkyls of 1 to 18 carbon atoms or more, such as methyl,ethyl, propyl, isopropyl, butyl, octenyl, cyclohexyl, phenyl, benzyl,tolyl and allyl.

In one embodiment, R groups are selected from C₁ to C₄ alkyls andhydrogen and R⁰ groups are selected from hydrogen, methyl, ethyl andpropyl.

Specific examples of X are methoxy, ethoxy, isobutoxy, propoxy,isopropoxy, acetoxy, oximato and monovalent hydroxyalkoxy groups derivedfrom diols, —O(R⁰CR⁰)_(f)OH where f is defined above, such as2-hydroxyethoxy, 2-hydroxypropoxy, 3-hydroxy-2,2-dimethylpropoxy,3-hydroxypropoxy, 3-hydroxy-2-methylpropoxy, 3-hydroxybutoxy,4-hydroxy-2-methylpent-2-oxy, and 4-hydroxybut-1-oxy. X may also be amonovalent alkyl group, such as methyl and ethyl.

In a specific embodiment, X is one of methoxy, ethoxy, acetoxy, methyl,ethyl, 2-hydroxyethoxy, 2-hydroxypropoxy, 3-hydroxy-2,2-dimethylpropoxy,3-hydroxypropoxy, 3-hydroxy-2-methylpropoxy, 3-hydroxybutoxy,4-hydroxy-2-methylpent-2-oxy, and 4-hydroxybut-1-oxy.

Specific examples of Z^(b) and Z^(c) are the divalent alkoxy groupsderived from diols such as ethylene glycol, propylene glycol, neopentylglycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol,2-methyl-2,4-pentanediol, 1,4-butanediol, cyclohexane dimethanol andpinacol. The divalent alkoxy groups derived from ethylene glycol,propylene glycol, neopentyl glycol, 1,3-propanediol,2-methyl-1,3-propanediol, 1,3-butanediol and 2-methyl-2,4-pentanediolare preferred.

In an embodiment of the present invention, the Z^(b) and Z^(c) aredivalent alkoxy groups derived from 1,3-propanediol,2-methyl-1,3-propanediol, 1,3-butanediol, and 2-methyl-2,4-pentanediol.

The cyclic dialkoxy content of the silanes herein should be keptsufficiently high relative to the total dialkoxy content present toprevent excessive crosslinking, which would lead to gellation. Excessivecrosslinking can also be avoided if X in the structure, as indicated bythe coefficient u, is large. In one embodiment, the v and w in Formulae(10) and (11) are such that the ratio v/w is between 0 and 10. Inanother embodiment, u is from 1 to about 2 with the proviso thatu+v+2w=3.

Representative examples of the organofunctional silanes of the presentinvention that contain cyclic and/or bridging dialkoxysilyl groups andfree and blocked mercapto groups include, but are not limited to,thioacetic acid2-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-ethylester; thioacetic acid3-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-propylester; thiobutyric acid3-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-propylester; octanethioic acid3-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-propylester; octanethioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4,4,6-trimethyl-[1,3,2]dioxasilinan-2-yloxy]-1,1-dimethyl-butoxy}-4,4,6-trimethyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;octanethioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4-methyl-[1,3,2]dioxasilinan-2-yloxy]-butoxy}-4-methyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;undecanethioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4-methyl-[1,3,2]dioxasilinan-2-yloxy]-butoxy}-4-methyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;heptanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;heptanethioic acidS-[3-(2-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilepan-2-yl)-propyl]ester;thiopropionic acid3-{2-[3-((3-mercapto-propyl)-methyl-{2-methyl-3-[5-methyl-2-(3-propionylsulfanyl-propyl)-[1,3,2]dioxasilinan-2-yloxy]-propoxy}-silanyloxy)-2-methyl-propoxy]-5-methyl-[1,3,2]dioxasilepan-2-yl}-propylester; octanethioic acid3-{2-[3-((3-mercapto-propyl)-methyl-{2-methyl-3-[5-methyl-2-(3-octanoylsulfanyl-propyl)-[1,3,2]dioxasilinan-2-yloxy]-propoxy}-silanyloxy)-2-methyl-propoxy]-5-methyl-[1,3,2]dioxasilepan-2-yl}-propylester; octanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-(3-octanoylsulfanyl-propyl)-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;octanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;octanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[bis-(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-silanyloxy]-2-methyl-propoxy}-(3-mercapto-propyl)-(3-hydroxy-2-methyl-propoxy)-silanyloxy]-2-methyl-propoxy}-(3-hydroxy-2-methyl-propoxy)-silanyl)-propyl]ester;dimethyl-thiocarbamic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;dimethyl-dithiocarbamic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; dimethyl-dithiocarbamic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; thiocarbonic acid O-ethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;trithiocarbonic acid ethyl ester3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; trithiocarbonic acid ethyl ester3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; dithiobutyric acid3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; dithiobutyric acid3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; diethyl-dithiocarbamic acid3-((3-hydroxy-2-methyl-propoxy)-{(3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; diethyl-dithiocarbamic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; N-methyl-thiobutyrimidic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; N-methyl-thiobutyrimidic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; thiophosphoric acid O,O′-diethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;thiophosphoric acid O-ethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]esterO′-propyl ester; dithiophosphoric acid O-ethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]esterO′-propyl ester; trithiophosphoric acid S,S′-diethyl esterS″-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;tetrathiophosphoric acid diethyl ester3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; tetrathiophosphoric acid diethyl ester3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; tetrathiophosphoric acid ethyl ester3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester propyl ester; methyl-phosphonodithioic acid S-ethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;dimethyl-phosphinothioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester,and the like.

In another embodiment, the cyclic and bridging dialkoxy free and blockedmercaptofunctional silanes of the present invention include, but are notlimited to, octanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[bis-(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-silanyloxy]-2-methyl-propoxy}-(3-mercapto-propyl)-(3-hydroxy-2-methyl-propoxy)-silanyloxy]-2-methyl-propoxy}-(3-hydroxy-2-methyl-propoxy)-silanyl)-propyl]ester;octanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;octanethioic acid3-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-propylester; octanethioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4,4,6-trimethyl-[1,3,2]dioxasilinan-2-yloxy]-1,1-dimethyl-butoxy}-4,4,6-trimethyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;octanethioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4-methyl-[1,3,2]dioxasilinan-2-yloxy]-butoxy}-4-methyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;undecanethioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4-methyl-[1,3,2]dioxasilinan-2-yloxy]-butoxy}-4-methyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;heptanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;heptanethioic acidS-[3-(2-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilepan-2-yl)-propyl]ester;thiopropionic acid3-{2-[3-((3-mercapto-propyl)-methyl-{2-methyl-3-[5-methyl-2-(3-propionylsulfanyl-propyl)-[1,3,2]dioxasilinan-2-yloxy]-propoxy}-silanyloxy)-2-methyl-propoxy]-5-methyl-[1,3,2]dioxasilepan-2-yl}-propylester; and octanethioic acid3-{2-[3-((3-mercapto-propyl)-methyl-{2-methyl-3-[5-methyl-2-(3-octanoylsulfanyl-propyl)-dioxasilinan-2-yloxy]-propoxy}-silanyloxy)-2-methyl-propoxy]-5-methyl-[1,3,2]dioxasilepan-2-yl}-propylester.

The organofunctional silane compositions of this invention that containcyclic and/or bridging silyl groups and both free and blocked mercaptangroups normally have a random distribution of free and blocked mercaptogroups within the individual silane. However, silanes in accordance withthe invention can be prepared in which the free and blocked mercaptangroups are segregated. This segregation will result in compositionswhere the nearest neighbors to a free mercaptan group are other freemercaptan groups or the nearest neighbors to a blocked mercaptan groupare other blocked mercaptan groups. The segregation of the free andblocked mercaptan groups can occur when blocked mercaptofunctionalcyclic and bridged silanes are physically mixed with freemercaptofunctional cyclic and bridged silanes.

Moreover, it is understood that these novel silane compositions can alsocontain free and blocked mercaptofunctional silane components thatcontain only monofunctional alkoxy groups. These free and blockedmercaptofunctional silanes containing only monofunctional alkoxy groupsmay be used as reagents in the preparation of the novel silanes of thepresent invention. However, it is understood that these monofunctionalalkoxy groups may contribute to VOC emissions during use. Moreover, itis understood that the partial hydrolyzates and/or condensates of thesecyclic and bridging dialkoxy blocked mercaptofunctional silanes (i.e.,cyclic and bridging dialkoxy blocked mercaptofunctional siloxanes and/orsilanols) may also be encompassed by the silanes herein, in that thesepartial hydrolyzates and/or condensates will be a side product of mostmethods of manufacture of the novel silanes of the present invention orcan occur upon storage, especially in humid conditions, or underconditions in which residual water remaining from their preparation isnot completely removed subsequent to their preparation.

Furthermore, partial to substantial hydrolysis of silanes (10) and (11)will form novel silanes that contain siloxane bonds, i.e.,Z^(b)=(—O—)_(0.5), and are encompassed by the silanes described herein.They can be deliberately prepared by incorporating the appropriatestoichiometry or an excess of water into the methods of preparationdescribed herein for the silanes. Silane structures herein encompassinghydrolyzates and siloxanes are described in the structures representedby Formulae (10) and (11) wherein the subscripts, v, ofZ^(b)=(—O—)_(0.5) and/or u of X═OH are substantive (i.e., substantiallylarger than zero). In one embodiment of the present invention, the ratioof siloxane bridging group, (—O—)_(0.5), to dioxy bridging group,[—O(R⁰CR⁰)_(f)O—]_(0.5), is within a range of from about 0 to about 1.In another embodiment, the ratio is within a range of from about 0 toabout 0.2.

In another embodiment of the present invention, the organofunctionalsilanes herein, including their mixtures, can be loaded on a particulatecarrier such as a porous polymer, carbon black, a siliceous materialsuch as or silica, etc., so that they are in solid form for addition torubber in a rubber compounding operation.

Organofunctional silanes (10) and (11) herein and mixtures thereof canbe prepared by the general preparative process described above of whichthere are numerous specific embodiments. Generally, the processembodiments for making one or a mixture of silanes (10) and (11) involvea transesterification reaction between one or more alkoxysilane formulae(1), (2) and (3) and one or more polyhydroxy-containing compounds offormula (6).

In one embodiment, the process for preparing the organofunctionalsilanes (10) and/or (11) comprises:

a.) transesterifying at least one blocked mercaptofunctional silane:[[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX₃)_(s)  (1)or[(X₃Si)_(q)-G²]_(a)-[Y—[S-G²-SiX₃]_(b)]_(c)  (2)wherein each occurrence of G¹, G², R, Y, X, a, b, c, j, k, p, q, r, ands are defined supra, and with the proviso that at least one of X is ahydrolyzable group, with at least one diol having the structureHO(R⁰CR⁰)_(f)OH, optionally in the presence of a transesterificationcatalyst; and,b) partially removing blocking groups, e.g., by the addition of a strongbase, to provide free mercaptan groups.

The first reaction can be carried out by reacting a mixture of blockedmercaptofunctional alkoxy silane and a diol at a molar ratio of about0.1 mole to about 3.0 moles of diol per 1 mole of silyl group to betransesterified. In another embodiment, the ratio can range from about1.0 to about 2.5 for a trialkoxy silyl group. The reaction can becarried out at a temperature ranging from about 0 to about 150° C. andall subranges therebetween while maintaining a pressure in the range offrom about 0.1 to about 2000 mm Hg absolute. In one embodiment, thetemperature can range from about 30° C. to about 90° C. and allsubranges therebetween. In another embodiment, the pressure can rangefrom about 1 to about 80 mm Hg absolute. As those skilled in the artwill recognize, excess diol can be utilized to increase reaction rate,but it is not necessary under these conditions as it may increase thecost. The reaction can be carried out by slowly adding diol to theblocked mercaptofunctional alkoxysilane at the desired reactiontemperature and vacuum. As the lower boiling mono alcohol is formed, itcan be removed from the reaction mixture by a distillation cycle.Removal of the mono alcohol helps drive the reaction to completion. Thereactions optionally can be catalyzed using a transesterificationcatalyst. Suitable tranesterification catalysts are strong protic acidswhose pK_(a) are below 5.0, transition metal complexes such as complexesof tin, iron, titanium and other metal catalysts. Catalysts suitable forthese reaction are disclosed in, “The Siloxane Bond, Physical Propertiesand Chemical Transformations”, M. G. Voronkov, V. P. Mileshkevich andYu. A. Yuzhelevskii, Consultants Bureau, a division of Plenum PublishingCompany, New York (1978), Chapter 5 and are included by referenceherein. Strong bases are generally unsuitable as transesterificationcatalysts since they promote the reaction of the blockedmercaptofunctional group with the diol and result in removal of theblocking group. The acid or metal catalysts can be used at a range ofabout 10 ppm to about 2 weight percent.

After the transestification reaction has reached completion, a strongbase may be added to partially remove blocking groups. In oneembodiment, suitable bases are those with a pK_(b) below 5.0 including,but not limited to, metal alkoxides, amides (—NR₂), mercaptides andcarbonates wherein the metal ion is lithium, sodium or potassium. Theamount of blocking group that is removed is dependent upon the amount ofbase added. It is understood that the strong base will first neutralizeany protic acids that were used in the transesterification reaction ofthe alkoxysilyl groups. Therefore, additional base in excess of thatamount needed to remove the desired amount of blocking group will berequired to first complete this neutralization and then remove theblocking group to the desired level. In one embodiment, the amount ofadditional base added is in a range of from about 0.0005 to about 0.05molar equivalents to the blocked mercapto group. In another embodiment,about 0.001 to about 0.01 molar equivalents of base are added.

After the blocking group has been partially removed, the final mixturecan optionally be buffered. Buffering the mixture will inhibit furtherremoval of blocking groups and will thus add to long-term productstability.

The products of the transesterification of blocked mercaptofunctionalsilane can comprise a considerable fraction of monomeric material inaddition to the formation of dimers and other cyclic and bridgedoligomers as illustrated by low viscosity reaction products.

These process for making the organofunctional silane compositions of theinvention can optionally employ an inert solvent. The solvent may serveas a diluent, carrier, stabilizer, refluxing aid or heating agent.Generally, any inert solvent that does not enter into the reaction oradversely affect the preparative process can be used. In one embodiment,the solvents are liquid under normal conditions and have a boiling pointbelow about 150° C. Examples of suitable solvents include aromatic,hydrocarbon, ether, aprotic, or chlorinated hydrocarbon solvents such astoluene, xylene, hexane, butane, diethyl ether, dimethylformamide,dimethyl sulfoxide, carbon tetrachloride, methylene chloride, and thelike.

In one embodiment of the present invention, the process oftransesterifying the alkoxysilane with diol can be conductedcontinuously. In the case of a continuous operation, the processcomprises:

-   -   a) reacting, in a thin film reactor, a thin film reaction medium        comprising at least one silane of Formula 5, at least one diol        and, optionally, transesterification catalyst, to provide        blocked mercaptosilane that contains a cyclic and/or bridged        dialkoxy group, and by-product mono alcohol;    -   b) vaporizing by-product mono alcohol from the thin film to        drive the reaction;    -   c) optionally, recovering by-product mono alcohol by        condensation;    -   d) partially removing blocking groups by the addition of base;    -   e) optionally, removing by-products of the deblocking step;    -   f) recovering the organofunctional silane reaction product(s);        and,    -   e) optionally, neutralizing organofunctional silane products to        improve the storage stability thereof.

The molar ratio of diol to blocked mercaptofunctional alkoxy silane usedin the continuous thin film process will depend upon the number ofalkoxy groups that are desired to be replaced with a diol group.Theoretically, a molar ratio of about 0.5 moles of diol is required peralkoxy-silyl group to be transesterified. For a trialkoxy silane, thestoichiometric equivalent molar ratio is about 1, wherein one diolreplaces two alkoxy groups. However, in many cases, only one of thehydroxyl groups of the diol reacts with the alkoxysilyl group. Thesediols are defined as X in Formulae (10) and (11). The diols, referred toherein as “hydroxyalkoxy”, reduce the viscosity and inhibit the gelationof the silane. As one skilled in the art will readily recognize, excessdiol can be utilized to increase reaction rates.

The method of forming the film can be any of those known in the art.Typical known devices include but are not limited to, falling film orwiped film evaporators. Minimum film thickness and flow rates willdepend on the minimum wetting rate for the film forming surface. Maximumfilm thickness and flow rates will depend on the flooding point for thefilm and device. The alcohol is vaporized from the film by heating thefilm, by reducing pressure over the film, or by a combination of both.In one embodiment, mild heating and reduced pressure are utilized toform the structures of this invention. Optimal temperatures andpressures (partial vacuum) for running this process will depend upon thespecific blocked mercaptofunctional silane's alkoxy groups and the diolused in the process. Additionally if an optional inert solvent is usedin the process, that choice will affect the optimal temperatures andpressures (partial vacuum) utilized. Examples of such solvents includethose listed above.

The by-product alcohol vaporized from the film is removed from thereactive distillation device by a standard partial vacuum-forming deviceand can be condensed, collected, and recycled as feed to otherprocesses. The silane product is recovered by standard means from thereactive distillation device as a liquid phase. If an inert solvent hasbeen used or if additional purification is necessary, the silane productmay be fed to another similar distillation device or distillation columnto effect that separation.

The addition of the base should occur after the transesterificationreaction between the diol and silane is complete. In one embodiment,this reaction can occur in a separate reaction vessel, so that the basedoes not neutralize the transesterification catalyst or catalyze theremoval of the blocking group. The transesterified intermediate productcan be continuous by transferred to a second reaction vessel, e.g., byuse of a transfer line and gravity, reduced or elevated pressure, ormechanical pump, to facilitate the process. In the second vessel, thedeblocking reaction can occur by the addition of base.

Optionally the transesterified reaction products can be neutralized toimprove product storage.

In another embodiment of the present invention, a process for preparingthe organofunctional silanes containing both free and blocked mercaptangroups comprises:

a) mixing at least one blocked mercaptofunctional silane of chemicalstructure:[[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX₃)_(s)  (1)and/or[(X₃Si)_(q)-G²]_(a)-[Y—[S-G²-SiX₃]_(b)]_(c)  (2)

-   -   -   with a mercaptofunctional silane of chemical formula            (HS)_(r)-G²-(SiX₃)_(s)  (3)

    -   wherein each occurrence of G¹, G², R, Y, X, a, b, c, j, k, p, q,        r, and s is as defined above and with the proviso that at least        one of X is a hydrolyzable group;

    -   b) reacting the silane mixture from step (a) with a diol        HO(R⁰CR⁰)_(f)OH wherein f and R⁰ are as defined above;        optionally in the presence of transesterification catalyst;

    -   c) removing by-product mono alcohol; and,

    -   d) optionally, neutralizing protonic transesterification        catalyst, if utilized, with a base.

The reaction conditions for transesterification of the mixture of freeand blocked mercaptofunctional silanes are described above for theblocked mercaptofunctional silane. However, after thetransesterification reaction is complete, the reaction mixture can beneutralized if a protic catalyst is used. Neutralization of the catalystwill improve the shelf-stability of the reaction products.

In one embodiment of the present invention, the amount of blockedmercaptofunctional silane of:[[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX₃)_(s)  (1)or[(X₃Si)_(q)-G²]_(a)-[Y—[S-G²-SiX₃]_(b)]_(c)  (2)and the amount of free mercaptofunctional silane of:(HS)_(r)-G²-(SiX₃)_(s)  (3)wherein each occurrence of G¹, G², R, Y, X, a, b, c, j, k, p, q, r, ands is as defined above and with the proviso that at least one of the X isa hydrolyzable group, are mixed in a molar ratio of silanes (1) and/or(2) to silane (3) in a range of from about 100:1 to about 0.2:1.

In another embodiment, the molar ratios of silane (1) and/or (2) tosilane (3) are in a range of from about 10:1 to about 1:1. If a proticcatalyst is used to promote the transesterification of the alkoxysilanewith diol, it may be useful to neutralize the catalyst with a base toinhibit the reaction of diol with blocked mercaptan groups. However,only a stoichiometric amount of base is required to neutralize theprotic catalyst. Larger amounts of base will promote the removal ofblocking group.

In yet another embodiment of the present invention, the process forpreparing the organofunctional silane containing both free and blockedmercaptan groups comprises:

-   -   a) transesterfying at least one blocked mercaptofunctional        silane of:        [[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX₃)_(s)  (1)        and/or        [(X₃Si)_(q)-G²]_(a)-[Y—[S-G²-SiX₃]_(b)]_(c)  (2)    -   wherein each occurrence of G¹, G², R, Y, X, a, b, c, j, k, p, q,        r, and s is as defined above, and with the proviso that at least        one of X is a hydrolyzable group, with at least one diol HO(R⁰C        R⁰)_(f)OH wherein f and R⁰ are as defined above, optionally, in        the presence of transesterification catalyst;    -   b) optionally, removing by-product mono alcohol from the        reaction mixture resulting from step (a);    -   c)transesterifying at least one mercaptofunctional silane of:        (HS)_(r)-G²-(SiX₃)_(s)  (3)    -   wherein each occurrence of G², X, r, and s is as defined above,        and with the proviso that at least one of X is a hydrolyzable        group, with at least one diol of structure HO(R⁰CR⁰)_(f)OH        wherein f and R⁰ are as defined above, optionally, in the        presence of transesterification catalyst;    -   d) optionally, removing by-product mono alcohol from the        reaction mixture resulting from step (c);    -   e) mixing product silane(s) from step (a) with product silane(s)        from step (c) to provide a mixture possessing a predetermined        amount of mercaptan and blocked mercaptan groups;    -   f) optionally, neutralizing the product mixture from step (e)        with a base if a protic catalyst was utilized.

In one embodiment of the present invention, the molar ratios of thesilane prepared in step a and the silane prepared in step d to formsilane f are in the range of about 100:1 to about 0.2:1. In anotherembodiment, the molar ratios of silane from step a and silane from stepd to form silane f are in a range from about 10:1 to about 1:1. It isunderstood that the desired ratio of blocked to free mercapto groups isdetermine by the mix ratio. The structure of the silane prepared may bebimodal in distribution of the free and blocked mercapto groups. Theoligomers and polymers formed may have segments where the nearestneighbors of the free mercapto group are other free mercapto groups andlikewise the nearest neighbors of the blocked mercapto group are otherblocked mercapto groups. The distribution of free and blocked mercaptogroups is therefore not random. The reaction conditions and processesfor transesterifying the free and blocked mercaptofunctional silanes aregiven above.

Further in accordance with the invention, a filled elastomer compositionis provided which comprises:

-   -   a) at least one elastomer containing carbon-carbon double bonds;    -   b) at least one inorganic particulate filler; and,    -   c) at least one organofunctional silane composition comprising        at least one organofunctional silane selected from the group        consisting of:    -   (i) mercaptosilane possessing at least one hydroxyalkoxysilyl        group and/or a cyclic dialkoxysilyl group,    -   (ii) blocked mercaptosilane possessing at least one        hydroxyalkoxysilyl group and/or a cyclic dialkoxysilyl group,    -   (iii) mercaptosilane dimer in which the silicon atoms of the        mercaptosilane units are bonded to each other through a bridging        dialkoxy group, each silane unit optionally possessing at least        one hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group,    -   (iv) blocked mercaptosilane dimer in which the silicon atoms of        the blocked mercaptosilane units are bonded to each other        through a bridging dialkoxy group, each silane unit optionally        possessing at least one hydroxyalkoxysilyl group or a cyclic        dialkoxysilyl group,    -   (v) silane dimer possessing a mercaptosilane unit the silicon        atom of which is bonded to the silicon atom of a blocked        mercaptosilane unit through a bridging dialkoxy group, each        silane unit optionally possessing at least one        hydroxyalkoxysilyl group or a cyclic dialkoxysilyl group,    -   (vi) mercaptosilane oligomer in which the silicon atoms of        adjacent mercaptosilane units are bonded to each other through a        bridging dialkoxy group, the terminal mercaptosilane units        possessing at least one hydroxyalkoxysilyl group or a cyclic        dialkoxysilyl group,    -   (vii) blocked mercaptosilane oligomer in which the silicon atoms        of adjacent blocked mercaptosilane units are bonded to each        other through a bridging dialkoxy group, the terminal        mercaptosilane units possessing at least one hydroxyalkoxysilyl        group or a cyclic dialkoxysilyl group, and    -   (viii) silane oligomer possessing at least one mercaptosilane        unit and at least one blocked mercaptosilane unit, the silicon        atoms of adjacent silane units being bonded to each other        through a bridging dialkoxy group, the terminal silane units        possessing at least one hydroxyalkoxysilyl group or a cyclic        dialkoxysilyl group, with the proviso that,    -   where the composition contains one or more of (i), (iii) and        (vi), the composition additionally contains one or more of (ii),        (iv), (v), (vii) and (viii), and where the composition contains        one or more of (ii), (iv) and (vii), the composition        additionally contains one or more of (i), (iii), (v), (vi) and        (viii).

In one embodiment of the foregoing filled elastomer composition, theorganofunctional silane composition comprises at least one of:[[[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX_(u)Z^(b) _(v)Z^(c)_(w))_(s)]_(m)[(HS)_(r)-G²-(SiX_(u)Z^(b) _(v)Z^(c) _(w))_(s)]_(n)  (10)and/or[[(X_(v)Z^(b) _(v)Z^(c) _(w)Si)_(q)-G²]_(a)-[Y—[S-G²-SiX_(u)Z^(b)_(v)Z^(c) _(w)]_(b)]_(c)]_(m)[(HS)_(r)-G²-(SiX_(u)Z^(b) _(v)Z^(c)_(w))_(s)]_(n)  (11)wherein:

each occurrence of Y is independently a polyvalent species (Q)_(z)A(=E),each wherein an atom (A) attached to an unsaturated heteroatom (E) isattached to a sulfur, which in turn is linked by means of a group G² toa silicon atom;

each occurrence of R is independently selected from the group consistingof hydrogen, straight, cyclic or branched alkyl that may or may notcontain unsaturation, alkenyl groups, aryl groups, and aralkyl groups,wherein each R, other than hydrogen, preferably contains from 1 to 18carbon atoms;

each occurrence of G¹ is independently selected from the groupconsisting of monovalent and polyvalent groups derived by substitutionof alkyl, alkenyl, aryl, or aralkyl wherein G¹ contains from 1 to about30 carbon atoms, with the proviso that if G¹ is univalent, G¹ can behydrogen;

each occurrence of G² is independently selected from the groupconsisting of monovalent and polyvalent groups derived by substitutionof alkyl, alkenyl, aryl, or aralkyl wherein G¹ contains from 1 to about30 carbon atoms;

each occurrence of X is independently selected from the group consistingof —Cl, —Br, RO—, RC(═O)O—, R₂C═NO—, R₂NO—, R₂N—, —R, HO(R⁰CR⁰)_(f)O—,wherein each R is as above and each occurrence of R⁰ is independentlygiven by one of the members listed above for R;

each occurrence of Z^(b), which forms a bridging structure between twosilicon atoms, is independently selected from the group consisting of(—O—)_(0.5), and [—O(R⁰CR⁰)_(f)O—]_(0.5), wherein each occurrence of R⁰is independently given by one of the members listed above for R;

each occurrence of Z^(c), which forms a cyclic structure with a siliconatom, is independently given by —O(R⁰CR⁰)_(f)O— wherein each occurrenceof R⁰ is independently given by one of the members listed above for R;

each occurrence of Q is independently selected from the group consistingof oxygen, sulfur, and (—NR—);

each occurrence of A is independently selected from the group consistingof carbon, sulfur, phosphorus, and sulfonyl;

each occurrence of E is independently selected from the group consistingof oxygen, sulfur, and (—NR—);

each occurrence of the subscripts, a, b, c, f j, k, m, n, p, q, r, s, u,v, w, and z is independently given by a is 0 to about 7; b is 1 to about3; c is 1 to about 6; f is 1 to about 15, j is 0 to about 1, but j maybe 0 only if p is 1; k is 1 to 2, with the provisos that

if A is carbon, sulfur, or sulfonyl, then (i) a+b=2 and (ii) k=1;

if A is phosphorus, then a+b=3 unless both (i) c>1 and (ii) b=1, inwhich case a=c+1; and

if A is phosphorus, then k is 2;

m is 1 to about 20, n is 1 to about 20, p is 0 to 5, q is 0 to 6; r is 1to 3; s is 1 to 3; u is 0 to 3; v is 0 to 3; w is 0 to 1 with theproviso that u+v+2w=3; z is 0 to about 3; and with the proviso that theeach of the above structures contains at least one hydrolysable group,Z^(b) or Z^(c), that is a difunctional alkoxy group.

Also within the scope of the invention are articles of manufacture,particularly tires, made from the foregoing filled elastomercompositions. The invention offers a means for significantly reducingvolatile organic compound (VOC) emissions during rubber manufacture andimproving the coupling between the organic polymers and inorganicfillers.

The novel organofunctional silane-based compositions described hereinare useful as coupling agents between elastomeric resins (i.e., rubbers)and inorganic fillers. The organofunctional silane compositions areunique in that the high efficiency of the mercaptan group can beutilized without the detrimental side effects typically associated withthe use of mercaptosilanes, such as high processing viscosity, less thandesirable filler dispersion, premature curing (scorch), and odor. Thesebenefits are obtained because the mercaptan group is part of a highboiling compound that liberates diol or higher polyhydroxy-containingcompound upon use. The combination of free and blocked mercapto groupsin this silane-based composition allow for a controlled amount ofcoupling to the organic polymer during the compounding of the rubber.During this non-productive mixing step, the cyclic and/or bridgedalkoxysilyl groups may react with the filler and essentially only thefree mercaptan groups may react with the rubber. The blocked mercaptangroups remain essentially inactive and are available to help dispersethe inorganic filler during the rubber compounding operation. Thus, acontrolled amount of coupling of the filler to the polymer occurs duringmixing thereby minimizing the undesirable premature curing (scorch) andthe associated undesirable increase in viscosity, while promoting theend-use properties such as reinforcing index, which is an indicator ofwear. Thus, one can achieve better cured filled rubber properties suchas a balance of high modulus and abrasion resistance, resulting from theavoidance or lessening of premature curing.

The organofunctional silane-based compositions herein providesignificant advantages over traditional coupling agents that have foundextensive use in the rubber and tire industries. These silanes usuallycontain in their molecular structures three ethoxy groups on eachsilicon atom, which results in the release of up to three moles ofsimple monohydroxy alcohol, e.g., ethanol for each silane equivalentduring the rubber manufacturing process in which the silane couples tothe filler. The release of this mono alcohol is a great disadvantagebecause it is flammable and therefore poses a threat of fire, andbecause it contributes so greatly to volatile organic compound (VOC)emissions and is therefore potentially harmful to the environment. Theorganofunctional silane-based compositions described herein eliminate orgreatly mitigate this problem by reducing volatile mono alcoholemissions to only one, less than one, and even essentially zero moles ofsuch alcohol per silane equivalent. They accomplish this because thesilane alkoxy groups are replaced with polyhydroxy alcohols, e.g., diolderived bridging groups and thus such polyhydroxy alcohols are releasedduring the rubber manufacture process in place of much, or nearly all,of the mono alcohol released. Diols, e.g., having boiling points well inexcess of rubber processing temperatures, are not vaporized out of therubber during the rubber manufacture process, as is the case, e.g., withethanol, but are retained by the rubber where they migrate to the silicasurface due to their high polarity and become hydrogen bonded to thesurfaces of siliceous fillers such as silicas. The presence of diols onsilica surfaces leads to further advantages not obtainable with ethanol(due to its volatility and ejection during the rubber compoundingprocess) in the subsequent cure process, in which such presence preventsthe silica surface from binding the curatives and thereby interferingwith the cure. Traditional silanes not based on diols require morecuratives to counter losses due to silica binding.

The addition of hydrocarbon-based diols to the rubber compoundingformulation prior to and/or concurrent with the addition of curatives isof advantage for the efficient utilization of the curatives, inparticular, and polar substances, such as, but not limited to, amines,amides, sulfenamides, thiurams, and guanidines. Whether diols areexclusively added in the form of diol-derived silanes or as free diolsin combination with the silane coupling agents, the polarity of thediols is of advantage to the rubber compounding process. These polarsubstances tend to migrate to the filler surface due to dipoleinteractions with the filler. This tends to make them unavailable withinthe organic polymer matrix, where their functions include plasticizationof the filled elastomer and acceleration, or retardation, of the curingreactions. The hydrocarbon-based diols enhance the function of thecuratives by interfering with their tendency to bind to the silicasurface thereby forcing them into the rubber matrix to perform theirfunction. The hydrocarbon-based diols accomplish this by themselvesbeing very polar, and thereby by themselves binding to the fillersurface, leaving less room for the curatives to bind to filler. Thehydrocarbon-based diols thus act as curative displacing agents from thefiller.

The short chain of the hydrocarbon-based diols further enhances theirfunction by a chelate effect. In one embodiment, the number of carbonatoms between the hydroxide groups of Z^(c) and/or Z^(b) herein areimportant and are defined by the divalent radical —O(R⁰CR⁰)_(f)O—,wherein each occurrence of f is 2 or 3. These chains of two or threecarbon atoms between the two OH groups of the diol promote the formationof 5- or 6-membered rings when both oxygen atoms bind to a commonsilicon atom of the silanes of Formulae (10) and (11). This dual bindingto a common center, known, and referred to herein as the chelate effect,increases the amount of cyclic dialkoxysilyl group and inhibits theformation of gel. After reactions with the silica in the rubbercompounding step, the diols that have been released have a high affinityto the filler because they can chelate with the metal or silicon atom onthe filler surface thereby enhancing their ability to prevent thebinding of the curatives to the filler.

The hydrocarbon-based diols used herein are superior to ether- and/orpolyether-based monofunctional alcohols or difunctional alcohols (diols)because the lack of the ether functionality of the hydrocarbon baseddiols avoids the problems typically encountered with ethers. Theseproblems include high toxicity, their tendency for spontaneous peroxideformation, and high chain lengths between OH groups. Spontaneousperoxide formation is a problem because it is difficult to prevent andbecause the peroxides represent flammability hazards. Furthermore,peroxides will decompose when heated to provide free radicals which caninitiate unwanted side reactions in the rubber polymers. These sidereactions include peroxide-induced cure in which polymer chains arecrosslinked. This can lead to premature, excess, and variablecrosslinking during or prior to cure. The excess crosslinking can leadto inferior properties in the rubber, premature crosslinking can lead toscorch, and the variability makes it hard to fabricate a reproduciblerubber composition and any articles of manufacture derived thereof.

The excess chain lengths of the ether-containing diols forces chelationby the two OH groups to involve ring sizes of at least about 8 atoms,which is well beyond the optimum 5 or 6, accessible to hydrocarbon baseddiols. Chelation involving an OH group and an ether, which would givethe optimum 5 or 6 membered rings, is not as strong as chelation withthe two OH groups accessible to the hydrocarbon based diols because theOH groups are less sterically hindered and because the OH groups aremore active at forming hydrogen bond interactions, which are key tobinding the diols to the filler surface.

An important advantage of the silanes herein is that the by-products ofthe silane coupling process are themselves of utility in enhancing therubber compounding process, the value of the resulting rubbercompositions, and/or any articles of manufacture employing the rubbercompositions. Thus, the blocked mercaptan groups of the silanes of thepresent invention not only retards coupling of silane to polymer duringmixing but also assists in the dispersion of the filler into the polymerduring mixing by reducing the ability of the surface hydroxyl or metaloxides to form hydrogen bonds between filler particles, therebyenhancing the ease and completeness of filler dispersion and retardingthe reversal of this process, namely, filler reagglomeration. Inaddition, the diols released from the silane's silicon atoms during theprocess of coupling to the filler are not just shed as a waste product,but perform an important follow-up function, specifically, enhancing theefficiency of the curatives, as previously described.

An unexpected result of the organofunctional silanes of the presentinvention is the long scorch times for uncured filled elastomerscontaining silanes (10) and (11). The high levels of mercapto-functionalgroups that are present in these silanes would normally produce veryshort scorch times. Long scorch times are desirable because they allowthe uncured rubber to be mixed with the fillers and other ingredients ina single pass and at higher temperatures, which facilitate fillerdispersion and uniform composition, without generating high and variableviscosities or partially cured compounds. Uncured filled elastomers withhigh viscosities are undesirable because they slow down the extrusionrates and fabrication of the articles. If the uncured rubber compound ispartially cured before the molding process begins, then the gelparticles resulting from premature crosslinking may generate defects andnegatively affect one or more of the physical properties of the curedelastomer.

In use, at least one of the organofunctional silane compositions thatcontain cyclic and/or bridging dialkoxysilyl groups and free and blockedmercapto groups is mixed with the organic polymer before, during, orafter the compounding of the filler into the organic polymer. In oneembodiment, the silanes are added before or during the compounding ofthe filler into the organic polymer because these silanes facilitate andimprove the dispersion of the filler. The total amount of silane presentin the resulting rubber composition should be about 0.05 to about 25parts by weight per hundred parts by weight of organic polymer (phr). Inanother embodiment, the amount of silane present in the rubber is fromabout 1 to 10 phr. Fillers can be used in quantities ranging from about5 to about 100 phr, more preferably from 25 to 80 phr.

When reaction of the mixture to couple the filler to the polymer isdesired, a deblocking agent is added to the mixture to deblock theorganofunctional silane compositions that contain cyclic and/or bridgingdialkoxysilyl groups and free and blocked mercapto groups. Thedeblocking agent may be added at quantities ranging from about 0.1 toabout 5 phr; more preferably in the range of from about 0.5 to about 3phr. If alcohol or water are present in the mixture (as is common), acatalyst (e.g., tertiary amines, or Lewis acids) may be used to initiateand promote the loss of the blocking group by hydrolysis or alcoholysisto liberate the corresponding mercaptosilane. Alternatively, thedeblocking agent may be a nucleophile containing a hydrogen atomsufficiently labile such that hydrogen atom could be transferred to thesite of the original blocking group to form the mercaptosilane. Thus,with a blocking group acceptor molecule, an exchange of hydrogen fromthe nucleophile would occur with the blocking group of the blockedmercaptosilane to form the mercaptosilane and the correspondingderivative of the nucleophile containing the original blocking group.This transfer of the blocking group from the silane to the nucleophilecould be driven, for example, by a greater thermodynamic stability ofthe products (mercaptosilane and nucleophile containing the blockinggroup) relative to the initial reactants (organofunctional silanecompositions that contain cyclic and/or bridging dialkoxysilyl groupsand free and blocked mercapto groups and the nucleophile). For example,if the nucleophile were an amine containing an N—H bond, transfer of theblocking group from the organofunctional silane compositions thatcontain cyclic and/or bridging dialkoxysilyl groups and free and blockedmercapto groups would yield the mercaptosilane and one of severalclasses of amides corresponding to the type of blocking group used. Forexample, carboxyl blocking groups deblocked by amines would yieldamides, sulfonyl blocking groups deblocked by amines would yieldsulfonamides, sulfinyl blocking groups deblocked by amines would yieldsulfinamides, phosphonyl blocking groups deblocked by amines would yieldphosphonamides, and phosphinyl blocking groups deblocked by amines wouldyield phosphinamides. What is important is that regardless of theblocking group initially present on the cyclic and bridging dialkoxyblocked mercaptofunctional silane and regardless of the deblocking agentused, the initially substantially inactive (from the standpoint ofcoupling to the organic polymer) organofunctional silane compositionsthat contain cyclic and/or bridging dialkoxysilyl groups and free andblocked mercapto groups is substantially converted at the desired pointin the rubber compounding procedure to the active mercaptosilane. It isnoted that partial amounts of the nucleophile may be used (i.e., astoichiometric deficiency), if one were to only deblock part of theorganofunctional silane compositions that contain cyclic and/or bridgingdialkoxysilyl groups and free and blocked mercapto groups to control thedegree of vulcanization of a specific formulation.

Water typically is present on the inorganic filler as a hydrate or boundto the filler in the form of a hydroxyl group. The deblocking agent canbe added in the curative package or, alternatively, at any other stagein the compounding process as a single component. Examples ofnucleophiles would include any primary or secondary amines, or aminescontaining C═N double bonds, such as imines or guanidines; with theproviso that said amine contains at least one N—H (nitrogen-hydrogen)bond. Numerous specific examples of guanidines, amines, and imines wellknown in the art, which are useful as components in curatives forrubber, are cited in Rubber Chemicals; J. Van Alphen; Plastics andRubber Research Institute TNO, Delft, Holland; 1973. Some examplesinclude: N,N′-diphenylguanidine, N,N′,N″-triphenylguanidine,N,N′-di-ortho-tolylguanidine, ortho-biguanide, hexamethylenetetramine,cyclohexylethylamine, dibutylamine, and 4,4′-diaminodiphenylmethane. Anygeneral acid catalysts used to transesterify esters, such as Bronsted orLewis acids, could be used as catalysts.

The rubber composition need not be, but preferably is, substantiallyfree of functionalized siloxanes, especially those of the type disclosedin Australian Patent AU-A-10082/97, which is incorporated herein byreference. Most preferably, the rubber composition is free offunctionalized siloxanes.

In practice, sulfur vulcanized rubber products typically are prepared bythermomechanically mixing rubber and various ingredients in asequentially step-wise manner followed by shaping and curing thecompounded rubber to form a vulcanized product. First, for the aforesaidmixing of the rubber and various ingredients, typically exclusive ofsulfur and sulfur vulcanization accelerators (collectively “curingagents”), the rubber(s) and various rubber compounding ingredients areusually blended in at least one, and often (in the case of silica filledlow rolling resistance tires) two, preparatory thermomechanical mixingstage(s) in suitable mixers. Such preparatory mixing is referred to asnon-productive mixing or non-productive mixing steps or stages. Suchpreparatory mixing usually is conducted at temperatures in the range offrom about 140° C. to about 200° C. and often in the range of from about150° C. to about 180° C.

Subsequent to such preparatory mix stages, in a final mixing stage,sometimes referred to as a productive mix stage, deblocking agent (inthe case of this invention), curing agents, and possibly one or moreadditional ingredients, are mixed with the rubber compound orcomposition, typically at a temperature in a range of 50° C. to 130° C.,which is a lower temperature than those utilized in the preparatory mixstages to prevent or retard premature curing of the sulfur curablerubber, which is sometimes referred to as scorching of the rubbercomposition.

The rubber mixture, sometimes referred to as a rubber compound orcomposition, typically is allowed to cool, sometimes after or during aprocess intermediate mill mixing, between the aforesaid various mixingsteps, for example, to a temperature of about 50° C. or lower.

When it is desired to mold and to cure the rubber, the rubber is placedinto the appropriate mold at about at least 130° C. and up to about 200°C., which will cause the vulcanization of the rubber by the mercaptogroups on the mercaptosilane and any other free sulfur sources in therubber mixture.

By thermomechanical mixing, it is meant that the rubber compound, orcomposition of rubber and rubber compounding ingredients, is mixed in arubber mixture under high shear conditions where it autogeneously heatsup as a result of the mixing, primarily due to shear and associatedfriction within the rubber mixture in the rubber mixer. Several chemicalreactions may occur at various steps in the mixing and curing processes.

The first reaction is a relatively fast reaction and is consideredherein to take place between the filler and the alkoxysilane group ofthe cyclic and/or bridging dialkoxy blocked mercaptofunctional silanes.Such reaction may occur at a relatively low temperature, such as, forexample, about 120° C. The second and third reactions are consideredherein to be the deblocking of the cyclic and/or bridging dialkoxyblocked mercaptofunctional silanes and the reaction which takes placebetween the sulfur-containing portion of the silane (after deblocking),and the sulfur vulcanizable rubber at a higher temperature; for example,above about 140° C.

Another sulfur source may be used, for example, in the form of elementalsulfur as S₈. A sulfur donor is considered herein as a sulfur-containingcompound that liberates free, or elemental sulfur, at a temperature in arange of about 140° C. to about 190° C. Such sulfur donors may be, forexample, although are not limited to, polysulfide vulcanizationaccelerators and organosilane polysulfides with at least two connectingsulfur atoms in their polysulfide bridge. The amount of free sulfursource addition to the mixture can be controlled or manipulated as amatter of choice relatively independently from the addition of theaforesaid cyclic and bridging dialkoxy blocked mercaptofunctional silanecomposition.

Thus, for example, the independent addition of a sulfur source may bemanipulated by the amount of addition thereof and by sequence ofaddition relative to addition of other ingredients to the rubbermixture.

In an embodiment of the present invention, a rubber composition isprepared by a process comprising the sequential steps of:

-   -   (a) thermomechanically mixing, in at least one preparatory        mixing step, to a temperature of 140° C. to 200° C.,        alternatively to 140° C. to 190° C., for a total mixing time of        2 to 20, alternatively 4 to 15, minutes for such mixing step(s):    -   i) 100 parts by weight of at least one sulfur vulcanizable        rubber selected from conjugated diene homopolymers and        copolymers, and copolymers of at least one conjugated diene and        aromatic vinyl compound,    -   ii) 5 to 100, preferably 25 to 80, phr of particulate filler,        wherein the filler preferably contains from 1 to 85 weight        percent carbon black iii) 0.05 to 20 parts by weight filler of        at least one cyclic and/or bridging dialkoxy silane of the        present invention composition;    -   b) subsequently blending therewith, in a final thermomechanical        mixing step at a temperature to 50° C. to 130° C. for a time        sufficient to blend the rubber, preferably between 1 to 30        minutes, more preferably 1 to 3 minutes, at least one deblocking        agent at about 0.05 to 20 parts by weight of the filler and a        curing agent at 0 to 5 phr; and, optionally,    -   c) curing said mixture at a temperature in the range of from 130        to 200° C. for about 5 to 60 minutes.        The process may also comprise the additional steps of preparing        an assembly of a tire or sulfur vulcanizable rubber with a tread        comprised of the rubber composition prepared according to this        invention and vulcanizing the assembly at a temperature in a        range of 130° C. to 200° C.

Suitable organic polymers and fillers are well known in the art and aredescribed in numerous texts, of which two examples include TheVanderbilt Rubber Handbook; R. F. Ohm, ed.; R.T. Vanderbilt Company,Inc., Norwalk, Conn.; 1990 and Manual For The Rubber Industry; T.Kempermann, S. Koch, J. Sumner, eds.; Bayer A G, Leverkusen, Germany;1993. Representative examples of suitable polymers include solutionstyrene-butadiene rubber (SSBR), styrene-butadiene rubber (SBR), naturalrubber (NR), polybutadiene (BR), ethylene-propylene co- and ter-polymers(EP, EPDM), and acrylonitrile-butadiene rubber (NBR).

The rubber composition is comprised of at least one diene-basedelastomer, or rubber. Suitable conjugated dienes are isoprene and1,3-butadiene and suitable vinyl aromatic compounds are styrene andalpha methyl styrene. Thus, the rubber is a sulfur curable rubber. Suchdiene based elastomer, or rubber, may be selected, for example, from atleast one of cis-1,4-polyisoprene rubber (natural and/or synthetic), andpreferably natural rubber), emulsion polymerization preparedstyrene/butadiene copolymer rubber, organic solution polymerizationprepared styrene/butadiene rubber, 3,4-polyisoprene rubber,isoprene/butadiene rubber, styrene/isoprene/butadiene terpolymer rubber,cis-1,4-polybutadiene, medium vinyl polybutadiene rubber (35-50 percentvinyl), high vinyl polybutadiene rubber (50-75 percent vinyl),styrene/isoprene copolymers, emulsion polymerization preparedstyrene/butadiene/acrylonitrile terpolymer rubber andbutadiene/acrylonitrile copolymer rubber. An emulsion polymerizationderived styrene/butadiene (ESBR) may be used having a relativelyconventional styrene content of 20 to 28 percent bound styrene or, forsome applications, an ESBR having a medium to relatively high boundstyrene content, namely, a bound styrene content of 30 to 45 percent.Emulsion polymerization prepared styrene/butadiene/acrylonitrileterpolymer rubbers containing 2 to 40 weight percent bound acrylonitrilein the terpolymer are also contemplated as diene based rubbers for usein this invention.

The solution polymerization prepared SBR (SSBR) typically has a boundstyrene content in a range of 5 to 50, preferably 9 to 36, percent.Polybutadiene elastomer may be conveniently characterized, for example,by having at least a 90 weight percent cis-1,4-content.

Representative examples of suitable filler materials include metaloxides, such as silica (pyrogenic and precipitated), titanium dioxide,aluminosilicate, and alumina, siliceous materials, including clays andtalc, and carbon black. Particulate, precipitated silica is alsosometimes used for such purpose, particularly in connection with asilane. In some cases, a combination of silica and carbon black isutilized for reinforcing fillers for various rubber products, includingtreads for tires. Alumina can be used either alone or in combinationwith silica. The term “alumina” can be described herein as aluminumoxide, or Al₂O₃. The fillers may be hydrated or in anhydrous form. Useof alumina in rubber compositions is known, see, for example, U.S. Pat.No. 5,116,886 and EP 631 982.

The organofunctional silane compositions that contain cyclic and/orbridging dialkoxysilyl groups and free and blocked mercapto groups maybe premixed, or pre-reacted, with the filler particles or added to therubber mix during the rubber and filler processing, or mixing stage. Ifthe silane and filler are added separately to the rubber mix during therubber and filler mixing, or processing stage, it is considered that theorganofunctional silane compositions that contain cyclic and/or bridgingdialkoxysilyl groups and free and blocked mercapto groups then couple insitu to the filler.

The vulcanized rubber composition should contain a sufficient amount offiller to contribute a reasonably high modulus and high resistance totear. The combined weight of the filler may be as low as about 5 to 100phr, but is more preferably from 25 to 85 phr.

In one embodiment of the present invention, precipitated silica isutilized as filler. The silica filler herein may as characterized byhaving a BET surface area, as measured using nitrogen gas, preferably inthe range of from about 40 to about 600 m²/g, and more preferably in arange of from about 50 to about 300 m²/g. The BET method of measuringsurface area is described in the Journal of the American ChemicalSociety, Volume 60, page 304 (1930). The silica typically may also becharacterized by having a dibutylphthalate (DBP) absorption value in arange of from about 100 to about 350, and more usually from about 150 toabout 300. Further, useful silica fillers, as well as the aforesaidalumina and aluminosilicate fillers, may be expected to have a CTABsurface area in a range of from about 100 to about 220 m²/g. The CTABsurface area is the external surface area as evaluated by cetyltrimethylammonium bromide with a pH of 9. The method is described inASTM D 3849.

Mercury porosity surface area is the specific surface area determined bymercury porosimetry. For such technique, mercury is penetrated into thepores of the sample after a thermal treatment to remove volatiles.Set-up conditions may be suitably described as using a 100 mg sample;removing volatiles during 2 hours at 105° C. and ambient atmosphericpressure; and ambient to 2000 bars pressure measuring range. Suchevaluation may be performed according to the method described inWinslow, et al. in ASTM bulletin, p. 39 (1959) or according to DIN66133. For such an evaluation, a CARLO-ERBA Porosimeter 2000 may beused. The average mercury porosity specific surface area for theselected silica filler should be in a range of 100 to 300 m²/g.

In one embodiment, a suitable pore size distribution for the silica,alumina and aluminosilicate according to such mercury porosityevaluation is considered herein to be: five percent or less of its poreshaving a diameter of less than about 10 nm; from about 60 to about 90percent of its pores have a diameter of from about 0 to about 100 nm;from 10 to about 30 percent of its pores having a diameter of from about100 to about 1,000 nm; and from about 5 to about 20 percent of its poreshave a diameter of greater than about 1,000 nm. In a second embodiment,the silica may be expected to have an average ultimate particle size,for example, in the range of from about 0.01 to about 0.05 μm asdetermined by electron microscopy, although the silica particles may beeven smaller, or possibly larger, in size. Various commerciallyavailable silicas may be considered for use herein such as, thoseavailable from PPG Industries under the HI-SIL trademark, in particular,HI-SIL 210, 243, etc.; silicas available from Rhone-Poulenc, e.g.,ZEOSIL 1165MP; silicas available from Degussa, e.g., VN2 and VN3, etc.and silicas available from Huber, e.g., HUBERSIL 8745.

Where it is desired for the rubber composition, which contains both asiliceous filler such as silica, alumina and/or aluminosilicates andalso carbon black reinforcing pigments, to be primarily reinforced withsilica as the reinforcing pigment, it is often preferable that theweight ratio of such siliceous fillers to carbon black is at least 3/1and preferably at least 10/1 and, thus, in a range of 3/1 to 30/1. Thefiller may comprise from about 15 to about 95 weight percentprecipitated silica, alumina and/or aluminosilicate and, correspondinglyfrom about 5 to about 85 weight percent carbon black, wherein the saidcarbon black has a CTAB value in a range of from about 80 to about 150.Alternatively, the filler may comprise from about 60 to about 95 weightpercent of said silica, alumina and/or aluminosilicate and,correspondingly, from about 40 to about 5 weight percent of carbonblack. The siliceous filler and carbon black may be pre-blended orblended together in the manufacture of the vulcanized rubber.

The rubber composition can be compounded by methods known in the rubbercompounding art, such as mixing the various sulfur-vulcanizableconstituent rubbers with various commonly used additive materials as,for example, curing aids such as sulfur, activators, retarders andaccelerators, processing additives such as oils, resins e.g., tackifyingresins, silicas, plasticizers, fillers, pigments, fatty acid, zincoxide, waxes, antioxidants and antiozonants, peptizing agents, andreinforcing materials such as, for example, carbon black, and the like.Depending on the intended use of the sulfur vulcanizable and sulfurvulcanized material (rubbers), the additives mentioned above areselected and commonly used in conventional amounts.

The vulcanization can be conducted in the presence of an additionalsulfur vulcanizing agent. Examples of suitable sulfur vulcanizing agentsinclude, e.g., elemental sulfur (free sulfur) or sulfur donatingvulcanizing agents, for example, an amino disulfide, polymericpolysulfide or sulfur olefin adducts, which are conventionally added inthe final, productive, rubber composition mixing step. The sulfurvulcanizing agents (which are common in the art) are used, or added inthe productive mixing stage, in an amount ranging from about 0.4 toabout 3 phr, or even, in some circumstances, up to about 8 phr, with arange of from about 1.5 to about 2.5 phr, and in some cases from about 2to about 2.5 phr, being preferred.

Vulcanization accelerators, i.e., additional sulfur donors, may also beused. It will be appreciated that they may be, for example, of the type,such as, for example, benzothiazole, alkyl thiuram disulfide, guanidinederivatives, and thiocarbamates. Representative of such acceleratorsare, e.g., but not limited to, mercapto benzothiazole, tetramethylthiuram disulfide, benzothiazole disulfide, diphenylguanidine, zincdithiocarbamate, alkylphenoldisulfide, zinc butyl xanthate,N-dicyclohexyl-2-benzothiazolesulfenamide,N-cyclohexyl-2-benzothiazolesulfenamide,N-oxydiethylenebenzothiazole-2-sulfenamide, N,N-diphenylthiourea,dithiocarbamylsulfenamide, N,N-diisopropylbenzothiozole-2-sulfenamide,zinc-2-mercaptotoluimidazole, dithiobis(N-methyl piperazine),dithiobis(N-beta-hydroxy ethyl piperazine) and dithiobis(dibenzylamine). Other additional sulfur donors, include, e.g., thiuram andmorpholine derivatives. Representative of such donors include, e.g., butare not limited to, dimorpholine disulfide, dimorpholine tetrasulfide,tetramethyl thiuram tetrasulfide, benzothiazyl-2,N-dithiomorpholide,thioplasts, dipentamethylenethiuram hexasulfide anddisulfidecaprolactam.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system can be used, i.e., a primaryaccelerator. Conventionally and preferably, a primary accelerator(s) isused in total amounts ranging from about 0.5 to about 4, preferably fromabout 0.8 to about 1.5, phr. Combinations of a primary and a secondaryaccelerator might be used with the secondary accelerator being used insmaller amounts (e.g., from about 0.05 to about 3 phr) in order toactivate and to improve the properties of the vulcanizate. Delayedaction accelerators may be used. Vulcanization retarders can also beused. Suitable types of accelerators are amines, disulfides, guanidines,thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates andxanthates. Preferably, the primary accelerator is a sulfenamide. If asecond accelerator is used, the secondary accelerator is preferably aguanidine, dithiocarbamate or thiuram compound.

Typical amounts of tackifier resins, if used, can be from about 0.5 toabout 10 phr, usually from about 1 to about 5 phr. Typical amounts ofprocessing aids comprise from about 1 to about 50 phr. Such processingaids can include, e.g., aromatic, naphthenic and/or paraffinicprocessing oils. Typical amounts of antioxidants are from about 1 toabout 5 phr. Representative antioxidants include, e.g.,diphenyl-p-phenylenediamine and others, e.g., those disclosed in theVanderbilt Rubber Handbook (1978), pages 344-346. Typical amounts ofantiozonants, are from about 1 to about 5 phr. Typical amounts of fattyacids, if used, which can include stearic acid, are from about 0.5 toabout 3 phr. Typical amounts of zinc oxide are from about 2 to about 5phr. Typical amounts of waxes are from about 1 to about 5 phr. Oftenmicrocrystalline waxes are used. Typical amounts of peptizers are fromabout 0.1 to about 1 phr. Typical peptizers include, e.g.,pentachlorothiophenol and dibenzamidodiphenyl disulfide.

The rubber compositions of this invention can be used for variouspurposes. For example, they can be used for various tire compounds, shoesoles and other industrial goods. Such articles can be built, shaped,molded and cured by various known and conventional methods as is readilyapparent to those skilled in the art. One particularly usefulapplication of the rubber compositions herein is for the manufacture oftire treads. An advantage of tires, tire treads, or other articles ofmanufacture derived from the rubber compositions herein is that theysuffer from less VOC emissions during their lifetime and use as a resultof having been manufactured from a rubber compound that contains lessresidual silane ethoxy groups than do rubber compounds of the known andcurrently practiced art. This is a direct result of having useddialkoxy-functional silane coupling agents in their manufacture, whichcontain fewer or essentially no ethoxy groups on silicon, relative tothe silane coupling agents of the currently known and practiced art. Thelack or reduction of ethoxysilane groups in the coupling agents usedresults in fewer residual ethoxy groups on silicon after the article ofmanufacture is produced, from which less or no ethanol can be releasedby hydrolysis of the residual ethoxysilane groups by exposure of thearticle of manufacture to water during use.

The rubber compositions herein and the articles of manufacture derivabletherefrom as described herein are novel in that both containnon-silicon-containing ethoxy esters and esters of hydrocarbon-baseddiols, as well as the hydrocarbon based diols. Typical examples of suchspecies contained in the rubber compositions and articles of manufacturedescribed herein include octanoate, hexanoate, decanoate, and/ordodecanoate esters of diols such as propanediols, pentane diols,ethylene glycol, and propylene glycol. Additional species would includeethyl octanoate, ethyl hexanoate, ethyl decanoate, and/or ethyldodecanoate. These species possess polarities intermediate between thoseof the rubber polymers and the filler, thereby helping to stabilize thecompositions and articles of manufacture from filler reagglomeration andthe resulting degradation of the properties and performance parametersthereof.

All references cited herein are incorporated herein as they are relevantto the present invention.

The invention may be better understood by reference to the followingexamples in which the parts and percentages are by weight unlessotherwise indicated.

COMPARATIVE EXAMPLES 1-3

Comparative Examples 1-3 were prepared by mixing3-thiooctanoylpropyltriethoxysilane and 3-mercaptopropyltriethoxysilanein the ratio indicated in Table 1.

TABLE 1 Com- Com- parative parative Comparative Silane Example 1 Example2 Example 3 3-thiooctanoylpropyltriethoxysilane 100 92.7 85.41-mercaptopropyltriethoxysilane 0 7.3 14.6

EXAMPLE 1

3-thiooctanoylpropyltriethoxysilane (1101 g; 3.03 moles) was added to around-bottomed flask. Sulfuric acid (0.98 g) was added to the reactionflask and 2-methylpropane-1,3-diol (816.6 g; 9.06 moles) was added viaaddition funnel. The flask was heated to 50° C. under a vacuum of 50torr. Ethanol (367 g) was collected. A 21% ethanolic solution of sodiumethoxide (9.53 g) was added and the mixture was heated to 100-120° C.under atmospheric pressure for several hours.

EXAMPLE 2

3-thiooctanoylpropyltriethoxysilane (1101 g; 3.03 moles) was added to around-bottomed flask. Sulfuric acid (0.98 g) was added to the reactionflask and 2-methylpropane-1,3-diol (816.6 g; 9.06 moles) was added viaaddition funnel. The flask was heated to 50° C. under a vacuum of 50torr. Ethanol (367 g) was collected. A 21% ethanolic solution of sodiumethoxide (10.7 g) was added and the mixture was heated to 100-120° C.under atmospheric pressure for several hours.

EXAMPLE 3

3-thiooctanoylpropyltriethoxysilane (1101 g; 3.03 moles) was added to around-bottomed flask. Sulfuric acid (0.98 g) was added to the reactionflask and 2-methylpropane-1,3-diol (816.6 g; 9.06 moles) was added viaaddition funnel. The flask was heated to 50° C. under a vacuum of 50torr. Ethanol (367 g) was collected. A 21% ethanolic solution of sodiumethoxide (11.3 g) was added and the mixture was heated to 100-120° C.under atmospheric pressure for several hours.

EXAMPLE 4

3-Thiooctanoylpropyltriethoxysilane (293.5 g; 0.81 mole) and3-mercaptopropyltriethoxysilane (32.6 g, 0.12 mole) were added to around-bottomed flask. Sulfuric acid (0.29 g) was added to the reactionflask and 2-methylpropane-1,3-diol (254.6 g; 4.04 moles) was added viaaddition funnel. The flask was heated to 50° C. under a vacuum of 50torr. Ethanol (112.7 g) was collected. A 21% ethanolic solution ofsodium ethoxide (0.73 g) was added. 439.8 grams of product wererecovered.

EXAMPLE 5

3-Thiooctanoylpropyltriethoxysilane (276.6 g; 0.76 moles) and3-mercaptopropyltriethoxysilane (69.2 g; 0.25 moles) were added to around-bottomed flask. Sulfuric acid (0.31 g) was added to the reactionflask and 2-methylpropane-1,3-diol (238.5 g; 2.65 moles) was added viaaddition funnel. The flask was heated to 50° C. under a vacuum of 50torr. Ethanol (137.9 g) was collected. A 21% ethanolic solution ofsodium ethoxide (1.13 g) was added.

EXAMPLE 6

Component I was prepared by adding 3-thiooctanoylpropyltriethoxysilane(541.1 g; 1.49 moles) to a round-bottomed flask. Sulfuric acid (0.47 g)was added to the reaction flask and 2-methylpropane-1,3-diol (401.4 g;4.45 moles) was added via addition funnel. The flask was heated to 50°C. under a vacuum of 50 torr. Ethanol (185.9 g) was collected. A 21%ethanolic solution of sodium ethoxide (3.5 g) was added. Component IIwas prepared by adding 3-mercaptopropyltriethoxysilane (250 g; 0.91mole) to a round-bottomed flask. Sulfuric acid (0.26 g) was added to thereaction flask and 2-methylpropane-1,3-diol (283 g; 3.14 moles) wasadded via addition funnel. The flask was heated to 50° C. under a vacuumof 50 torr. Ethanol (126.7 g) was collected. A 21% ethanolic solution ofsodium ethoxide (1.24 g) was added. In a round-bottomed flask werecombined Component I (145.2 g) and Component II (54.8 g). The mixturewas stirred under nitrogen.

COMPARATIVE EXAMPLES 4-6; EXAMPLES 7-12

Cured rubber compositions in the form of plaques (Comparative Examples4-6 employing the silanes of Comparative Examples 1-3, respectively, andExamples 7-12 employing the silanes of Examples 1-6, respectively) wereprepared and their physical and dynamic properties measured.

A typical silica-rubber SBR formulation was used as described below inTable 2. Mixing was carried out in a 1550 ml Krupp intermeshing mixer.The silane loadings were 8.2 phr.

TABLE 2 Silica-Silane/Rubber Formulation PHR Components 103.2 sSBR (BunaVSL 5525-1) - (Bayer AG) 25 BR (Budene 1207) - (Goodyear) 80 silica -Zeosil 1165MP, (Rhodia) 8.2 Silane from Comparative Examples 1-3 andExamples 1-6 4.5 oil - Sundex 8125 (Sun Oil) 2.5 zinc oxide - Kadox 720C(ZincCorp.) 1.0 stearic acid - Industrene R (Witco, Crompton) 2.0 6PPD - Flexzone 7P (Uniroyal, Crompton) 1.5 Wax - Sunproof Improved(Uniroyal, Crompton) Final Mix Ingredients 1.4 Rubbermakers Sulfur 104,Harwick 1.7 CBS - Delac S (Uniroyal, Crompton) 2.0 DPG - (Uniroyal,Crompton)

The procedure for preparing a single non-productive mix is presented inTable 3 below.

TABLE 3 One Pass Procedure; Cooling with water @ 25° C., 68% fillfactor: Step Procedure 1 Add polymers, RDM (ram down mix) 60 seconds 2Add 50% silica, all silane, oil, RDM 60 seconds 3 Add remaining 50%silica, wax, RDM 90 seconds 4 Dust down, RDM 30 seconds 5 Add remainderof ingredients, RDM 60 seconds 6 Dust down, RDM to 160-170° C. (inapprox. 2 minutes) by increasing rotor speed 7 Hold at 170° C. (orhigher temperature) for 8 minutes by changing speeds on the mixer. 8Dump, sheet off roll mill @ 65-70° C. to coolThe procedure for preparing a single productive mix involved addingsulfur and accelerators (primary and secondary) into a masterbatchprepared as described in Table 3 on a two-roll mill at 65-70° C. Afterall the silica filler, silane and oil were incorporated into a givenmix, the rpm of the rotors was raised so as to achieve the desiredsilanization temperature. The mix was then held at that temperature for8 minutes. The mix procedures are shown in Table 3, above.

Curing and testing of the cured rubber compositions in the form ofplaques were carried out according to ASTM standards. In addition, smallstrain dynamic tests were carried out on a Rheometrics Dynamic Analyzer(ARES-Rheometrics Inc.). The specific curing procedure, measurements andmeasuring procedures were as follows:

Curing Procedure/Measurement Testing Standard Mooney viscosity andscorch ASTM D1646 Oscillating disc rheometry ASTM D2084 Curing of testplaques ASTM D3182 Stress-strain properties ASTM D412 Heat build-up ASTMD623

Dynamic Mechanical Properties:

Payne effect strain sweeps were carried out from dynamic strainamplitudes of 0.01% to about 25% shear strain amplitude at 10 Hz and 60°C. The dynamic parameters, G′_(initial), ΔG′, G″_(max), tan δ_(max) wereextracted from the non-linear responses of the rubber compounds at smallstrains. In some cases, steady state values of tan δ were measured after15 minutes of dynamic oscillations at strain amplitudes of 35% (at 60°C.). Temperature dependence of dynamic properties were also measuredfrom about −80° C. to +80° C. at small strain amplitudes (1 or 2%) at afrequency of 10 Hz. The results for the test plaques of ComparativeExamples 4-6 and Examples 7-12 are presented in Table 4.

TABLE 4 Physical and Dynamic Properties of Cured Rubber Compositions: ofComparative Examples 4-6 and Examples 7-12 Examples Comp Comp Comp Ex. 4Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Silane used: Comp.Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 1 Ex. 2 Ex. 3 % SHTitration 1.43 2.41 3.09 1.03 2.24 2.31 Mooney Viscosity @ 100° C. ML1 +4 59 62 64 64.38 64.52 65.36 62 64 65.22 Mooney Scorch @ 135° C. M_(V)24 29 31 30.16 32.40 34.49 29 31.0 32.12 MS1+, t₃, minutes 8.5 6.1 5.07.4 7.3 7.0 7.3 6.0 6.3 MS1+, t₁₈, minutes 13.2 10.0 7.5 9.48 9.13 8.259.4 7.5 8.05 Oscillating Disc Rheometer @ 149° C., 1° arc, 30 minutetimer M_(L), dNm 8.3 9.5 10.3 8.92 9.42 10.16 8.6 8.8 9.57 M_(H), dNm27.7 28.2 28.5 31.20 30.36 30.18 31.2 30.4 31.38 t_(s1), minutes 4.6 4.33.5 4.68 4.54 4.25 4.3 3.5 4.04 t90, minutes 15.4 14.2 11.1 9.69 9.398.76 8.7 7.3 7.98 M_(H), dNm-M_(L) 19.4 18.7 18.2 22.28 20.94 20.02 22.621.6 21.80 Physical Properties, cured t90 @ 149° C. Hardness, Shore A 5453 53 58 58 57 58 56 58 25% Modulus, MPa 0.68 0.68 0.73 0.923 0.8660.819 0.77 0.80 0.879 100% Modulus, MPa 1.53 1.65 1.76 2.42 2.29 2.152.10 2.20 2.35 300% Modulus, MPa 7.30 8.78 9.82 13.32 13.98 14.20 12.0213.36 14.03 Tensile, MPa 22.2 22.6 23.1 21.78 20.36 19.03 22.0 21.719.98 RI 300/25 10.74 12.91 13.45 14.43 16.14 17.34 15.6 16.7 15.96 RI300/100 4.78 5.32 5.58 5.50 6.10 6.60 5.7 6.1 5.97 Dynamic Properties inthe Cured State Non-linearity (0-10%) @ 60° C. G′, initial, MPa 2.512.67 2.23 2.15 2.02 2.87 Delta G′, MPa 1.06 1.19 0.84 0.79 0.69 1.35G″_(max), MPA 0.29 0.33 0.25 0.233 0.205 0.32 tan delta_(max) 0.14 0.140.13 0.126 0.121 0.14 Low Temperature Viscoelasticity tan delta, 0° C.0.54 0.55 0.54 0.568 0.560 0.55 tan delta, 60° C. 0.13 0.13 0.12 0.1190.113 0.12 G′, 0° C., MPa 5.50 5.42 4.65 5.20 4.77 5.54 G′, 60° C., MPa1.92 1.92 1.72 1.72 1.69 1.96

As shown by the data presented in Table 4, the organofunctional andcyclic and/or bridging dialkoxy silane compositions of the presentinvention (Examples 1-6) show equivalent or improved performance whilemaintaining the long scorch times necessary for mixing, extrusion andfabricating articles. These silane compositions also offer a significantbenefit in reducing the amounts of VOCs that are released.

COMPARATIVE EXAMPLES 7 AND 8

During the compounding of rubber, 3-thiooctanoylpropyltriethoxysilane(6.64 phr), 3-mercaptopropyltriethoxysilane (1.56 phr), and2-methyl-1,3-propanediol (2.0 phr) were added, as described in themixing procedure of Table 3, to provide the test plaque of ComparativeExample 8. The uncured filled elastomer of Comparative Example 7,exhibited very short scorch times, as shown in Table 5, infra.

EXAMPLE 13

Thiooctanoylpropyltriethoxysilane (213 g; 0.59 mole) was added to around-bottomed flask. Sulfuric acid (0.25 g) and trimethylolpropane (235g, 1.55 moles) were added to the reaction flask. The flask was heated to70° C. under a vacuum of 50 torr. The trimethylolpropane melted anddissolved. Ethanol (80 g) was collected. A 21% ethanolic solution ofsodium ethoxide (0.97 g) was added and the mixture was heated to100-120° C. under atmospheric pressure for several hours.

EXAMPLE 14

To a 2-liter round bottomed flask was charged3-octanoylthio-1-propyltriethoxysilane (602 grams; 1.65 moles) anddiethylene glycol (526 grams; 4.96 moles). A catalytic amount (0.8grams) of para-toluenesulfonic acid (PTSA) was then added to themixture. The 2-liter flask with its contents was then immediately placedonto a rotary evaporator. The contents were subject to rotaryevaporation using a mechanical pump as a vacuum source, a dry ice trapas a condenser, a needle valve as a flow regulator between the dry icetrap and vacuum pump, and a heated water bath as a dual source of heatand buoyancy. Rotary evaporation was begun with the water bath atambient temperature, which was gradually raised to and then maintainedat a maximum of 70° C. Rotary evaporation was continued until no morecondensation of ethanol was evident in the dry ice trap. The total timeof rotary evaporation was 3.5 hours. The quantity of ethanol collectedin the trap (213 grams; 4.63 moles) is consistent with 93%transesterification of the triethoxysilane group on the starting silaneto DEG functionality. This reactant product is designated Silane A.

To a 2-liter round bottomed flask was charged3-mercapto-1-propyltriethoxysilane (238 grams; 1.00 mole) and diethyleneglycol (318.4 grams; 3.00 moles). A catalytic amount (0.5 grams) ofpara-toluenesulfonic acid (PTSA) was then added to the mixture. The2-liter flask with its contents was then immediately placed onto arotary evaporator. The contents were subject to rotary evaporation usinga mechanical pump as a vacuum source, a dry ice trap as a condenser, aneedle valve as a flow regulator between the dry ice trap and vacuumpump, and a heated water bath as a dual source of heat and buoyancy.Rotary evaporation was begun with the water bath at ambient temperature,which was gradually raised to and then maintained at a maximum of 64° C.Rotary evaporation was continued until no more condensation of ethanolwas evident in the dry ice trap. The quantity of ethanol collected inthe trap (133 grams; 2.9 moles) is consistent with 97%transesterification of the triethoxysilane group on the starting silaneto DEG functionality. This reaction product is designated Silane B.

Into a 100 ml round bottom flask equipped with a mechanical stirrer wascharged Silane A (85 grams). Silane A was stirred at room temperatureand then slowly Silane B (15 grams) was added thereto. This mixture ofSilane A and B is designated Silane C.

EXAMPLE 15

Into a 100 ml round bottom flask equipped with a mechanical stirrer wascharged Silane A (65 grams). Silane A was stirred at room temperatureand then slowly Silane B (35 grams) was added. The mixture of Silane Aand B is designated Silane D.

EXAMPLE 16

To a 2-liter round bottomed flask was charged3-octanoylthio-1-propyltriethoxysilane (234 grams; 0.64 moles),3-mercapto-1-propyltriethoxysilane (76.7 grams; 0.32 moles), anddiethylene glycol (307 grams; 2.89 moles). A catalytic amount (0.4grams) of para-toluenesulfonic acid (PTSA) was then added to themixture. The 2-liter flask with its contents was then immediately placedonto a rotary evaporator. The contents were subject to rotaryevaporation using a mechanical pump as a vacuum source, a dry ice trapas a condenser, a needle valve as a flow regulator between the dry icetrap and vacuum pump, and a heated water bath as a dual source of heatand buoyancy. Rotary evaporation was begun with the water bath atambient temperature, which was gradually raised to and then maintainedat a maximum of 96° C. Rotary evaporation was continued until no morecondensation of ethanol was evident in the dry ice trap. The total timeof rotary evaporation was 4 hours and 30 minutes. The quantity ofethanol collected in the trap (129 grams; 2.8 moles) is consistent with97% transesterification of the triethoxysilane group on the startingsilane to DEG functionality. This reaction product is designated SilaneE.

Table 5 below sets forth the properties of the cured rubber test plaquesof Comparative Example 8 and examples 17-19.

TABLE 5 TABLE 5: Physical and Dynamic Properties of Cured RubberCompositions of Comparative Example 8 and Examples 17-19: Comp. Ex. 8Ex. 17 Ex. 18 Ex. 19 Silane Comp. Ex. 7 Ex. 14 Ex. 15 Ex. 16 % SHTitration 2.5 Mooney Viscosity @100° C. ML1 + 4 70.9 51.8 55.0 54.1Mooney Scorch @135° C. M_(V) 44.97 24.72 26.67 26.67 MS1+, t₃, minutes0.05 5.36 4.26 5.18 MS1+, t₁₈, minutes 10.25 7.43 6.10 7.25 OscillatingDisc Rheometer @ 149° C., 1° arc, 30 minute timer M_(L), dNm 8.42 7.578.82 8.34 M_(H), dNm 30.63 30.38 30.66 30.69 t_(s1), minutes 4.28 3.442.68 3.45 t90, minutes 13.21 7.79 6.60 8.21 M_(H), dNm-M_(L) 22.20 22.8121.84 22.35 Physical Properties, cured t90 @ 149° C. Hardness, Shore A53 Elongation, % 351 25% Modulus, MPa 0.96 100% Modulus, MPa 2.54 300%Modulus, MPa 15.86 Tensile, MPa 20.00 RI 300/25 16.45 RI 300/100 6.25

While the invention has been described with reference to a number ofexemplary embodiments, it will be understood by those skilled in the artthat various changes can be made and equivalents can be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications can be made to adapt a particular situationor material to the teachings of the invention without departing fromessential scope thereof. Therefore, it is intended that the inventionnot be limited to any particular exemplary embodiment disclosed herein.

1. A rubber composition comprising (a) at least one rubber component,(b) at least one particulate filler and (c) at least oneorganofunctional silane selected from the group consisting of:[[[(ROC(═O))_(p)-(G¹)_(j)]_(k)-Y—S]_(r)-G²-(SiX_(u)Z^(b) _(v)Z^(c)_(w))_(s)]_(m)[(HS)_(r)-G²-(SiX_(u)Z^(b) _(v)Z^(c) _(w))_(s)]_(n)  (10)and[[(X_(v)Z^(b) _(v)Z^(c) _(w)Si)_(q)-G²]_(a)-[Y-[S-G²-SiX_(u)Z^(b)_(v)Z^(c) _(w)]_(b)]_(c)]_(m)[(HS)_(r)-G²-(SiX_(u)Z^(b) _(v)Z^(c) _(w))_(s)]_(n)  (11) wherein: each occurrence of Y is independently selectedfrom a polyvalent species (Q)_(z)A(═E), wherein the atom (A) attached toan unsaturated heteroatom (E) is attached to a sulfur, which in turn islinked by means of a group G² to a silicon atom; each occurrence of R isindependently selected from the group consisting of hydrogen, straight,cyclic or branched alkyl that may or may not contain unsaturation,alkenyl groups, aryl groups, and aralkyl groups, wherein each R, otherthan hydrogen, contains from 1 to 18 carbon atoms; each occurrence of G¹is independently selected from the group consisting of monovalent andpolyvalent groups derived by substitution of alkyl, alkenyl, aryl, oraralkyl wherein G¹ can have from 1 to about 30 carbon atoms, with theproviso that if G¹ is univalent, G¹ can be hydrogen; each occurrence ofG² is independently selected from the group consisting of divalent orpolyvalent group derived by substitution of alkyl, alkenyl, aryl, oraralkyl wherein G² can have from 1 to 30 carbon atoms; each occurrenceof X is independently selected from the group consisting of —Cl, —Br,RO—, RC(═O)O—, R₂C═NO—, R₂NO—, R₂N—, —R, HO(R⁰CR⁰)_(f)O—, wherein each Ris as above and each occurrence of R⁰ is independently given by one ofthe members listed above for R; each occurrence of Z^(b), which forms abridging structure between two silicon atoms, is independently selectedfrom the group consisting of (—O—)_(0.5), and [—O(R⁰CR⁰)_(f)O—]_(0.5),wherein each occurrence of R⁰ is independently given by one of themembers listed above for R; each occurrence of Z^(c), which forms acyclic structure with a silicon atom, is independently given by—O(R⁰CR⁰)_(f)O— wherein each occurrence of R⁰ is independently given byone of the members listed above for R; each occurrence of Q isindependently selected from the group consisting of oxygen, sulfur, and(—NR—); each occurrence of A is independently selected from the groupconsisting of carbon, sulfur, phosphorus, and sulfonyl; each occurrenceof E is independently selected from the group consisting of oxygen,sulfur, and (—NR—); each occurrence of the subscripts, a, b, c, f, j, k,m, n, p, q, r, s, u, v, w, and z is independently given by a is 0 toabout 7; b is 1 to about 3; c is 1 to about 6; f is about 2 to about 15,j is 0 to about 1, but j may be 0 only if p is 1; k is 1 to 2, with theprovisos that if A is carbon, sulfur, or sulfonyl, then (i) a+b=2 and(ii) k=1; if A is phosphorus, then a+b=3 unless both (i) c>1 and (ii)b=1, in which case a=c+1; and if A is phosphorus, then k is 2; m is 1 toabout 20, n is 1 to about 20, p is 0 to 5, q is 0 to 6; r is 1 to 3; sis 1 to 3; u is 0 to 3; v is 0 to 3; w is 0 to 1 with the proviso thatu+v+2w=3; z is 0 to about 3; and with the proviso that the each of theabove structures contains at least one hydrolysable group, Z^(b) orZ^(c), that is a difunctional alkoxy group.
 2. The rubber composition ofclaim 1 wherein Y is selected from the group consisting of —C(═NR)—;—SC(═NR)—; —SC(═O)—; (—NR)C(═O)—; (—NR)C(═S)—; —OC(═O)—; —OC(═S)—;—C(═O)—; —SC(═S)—; —C(═S)—; —S(═O)—; —S(═O)₂—; —OS(═O)₂—; (—NR)S(═O)₂—;—SS(═O)—; —OS(═O)—; (—NR)S(═O)—; —SS(═O)₂—; (—S)₂P(═O)—; —(—S)P(═O)—;—P(═O)(—)₂; (—S)₂P(═S)—; —(—S)P(═S)—; —P(═S)(—)₂; (NR)₂P(═O)—;(—NR)(—S)P(═O)—; (—O)(—NR)P(═O)—; (—O)(—S)P(═O)—; (—O)₂P(═O)—;—(—O)P(═O)—; —(—NR)P(═O)—; (—NR)₂P(═S)—; (—NR)(—S)P(═S)—;(—O)(—NR)P(═S)—; (—O)(—S)P(═S)—; (—O)₂P(═S)—; —(—O)P(═S)—; and—(—NR)P(═S)—.
 3. The rubber composition of claim 2 wherein Y is —C(═O)—.4. The rubber composition of claim 3 wherein G¹ has a primary carbonatom attached to a carbonyl and is a C₁-C₁₈ alkyl.
 5. The rubbercomposition of claim 3 wherein G² is a divalent or polyvalent groupderived by substitution of C₁-C₁₂ alkyl.
 6. The rubber composition ofclaim 4 wherein G¹ is a monovalent straight chain group derived from aC₃-C₁₀, alkyl.
 7. The rubber composition of claim 5 wherein G² is adivalent or polyvalent group derived by substitution of a C₃-C₁₀ alkyl,pis 0, j is 1 and k is 1 and the ratio of m to n is from about 20:1 toabout 3:1.
 8. The rubber composition of claim 6 wherein G¹ is amonovalent straight chain group derived from a C₆-C₈ alkyl.
 9. Therubber composition of claim 7 wherein G² is a divalent or polyvalentgroup derived by substitution of a C₃-C₆ alkyl, p is 0, j is 1 and k is1 and the ratio of m to n is from about 10:1 to about 4:1.
 10. Therubber composition of claim 1 wherein G¹ is CH₃(CH₂)_(g)— and g is from1 to about
 29. 11. The rubber composition of claim 10 wherein G¹ isselected from the group consisting of methyl, ethyl, propyl, hexyl,heptyl, benzyl, phenyl, octyl and dodecyl.
 12. The rubber composition ofclaim 1 wherein G² is —(CH₂)_(g)— and g is from 1 to about
 29. 13. Therubber composition of claim 12 wherein G² is selected from the groupconsisting of methylene, ethylene, propylene, butylenes and hexylene.14. The rubber composition of claim 1 wherein the sum of the carbonatoms for G¹ and G² groups is from about 3 to about
 18. 15. The rubbercomposition of claim 14 wherein the sum of the carbon atoms for G¹ andG² is from about 6 to about
 14. 16. The rubber composition of claim 11wherein G¹ is selected from the group consisting of —CH₂—, —CH₂CH₂—,—CH₂CH₂CH₂—; —CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—; —CH₂(CH₂)_(i)CH(CH₃)—, whereini is 0 to about 16; —CH₂CH₂C(CH₃)₂CH₂—; —CH₂CH(CH₃)CH₂—;—CH₂CH₂(C₆H₄)CH₂CH₂—; —CH₂CH₂(C₆H₄)CH(CH₃)—;—CH₂CH(CH₃)(C₆H₄)CH(CH₃)CH₂—; —CH₂CH₂CH₂CH₂—; —CH₂CH₂CH(CH₃)—;—CH₂CH(CH₂CH₃)—; —CH₂CH₂CH₂CH(CH₃)—; —H₂CH₂CH(CH₂CH₃)—;—CH₂CH(CH₂CH₂CH₃)—; —CH₂CH(CH₃)CH₂CH₂—; —CH₂CH(CH₃)CH(CH₃)—;—CH₂C(CH₃)(CH₂CH₃)—; —CH₂CH₂CH(CH₃)CH₂—; —CH₂CH₂C(CH₃)₂—;—CH₂CH[CH(CH₃)₂]—; —CH₂CH₂—norbornyl-, —CH₂CH₂cyclohexyl-; any of thediradicals obtainable from norbornane, cyclohexane, cyclopentane,tetrahydrodicyclopentadiene, or cyclododecene by loss of two hydrogenatoms; the structures derivable from limonene, —CH₂CH(4—CH₃—1—C₆H₉—)CH₃;—CH₂CH₂(vinylC₆H₉)CH₂CH₂—; —CH₂CH₂(vinylC₆H₉)CH(CH₃)—,—CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH₂CH₂—; —CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH(CH₃)—;—CH₂C[CH₂CH₂CH═C(CH₃)₂](CH₂CH₃)—; —CH₂CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH₂—;—CH₂CH₂(C—)(CH₃)[CH₂CH₂CH═C(CH₃)₂]; —CH₂CH[CH(CH₃)[CH₂CH₂CH═C(CH₃)₂]]—;—CH₂CH(CH═CH₂)CH₂CH₂CH₂C(CH₃)₂—, —CH₂CH(CH═CH₂)CH₂CH₂CH[CH(CH₃)₂]—,—CH₂C(═CH—CH₃)CH₂CH₂CH₂C(CH₃)₂—, —CH₂C(═CH—CH₃)CH₂CH₂CH[CH(CH₃)₂]—,—CH₂CH₂C(═CH₂)CH₂CH₂CH₂C(CH₃)₂—, —CH₂CH₂C(═CH₂)CH₂CH₂CH[CH(CH₃)₂]—,—CH₂CH═C(CH₃)₂CH₂CH₂CH₂C(CH₃)₂—, and —CH₂CH═C(CH₃)₂CH₂CH₂CH[CH(CH₃)₂].17. The rubber composition of claim 12 wherein G² is selected from thegroup consisting of —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—;—CH₂CH₂CH₂CH₂CH₂CH₂CH₂CH₂—, CH₂(CH₂)_(i)CH(CH₃)—, where i is 0 to about16; —CH₂CH₂C(CH₃)₂CH₂—; —CH₂CH(CH₃)CH₂—; —CH₂CH₂(C₆H₄)CH₂CH₂—;—CH₂CH₂(C₆H₄)CH(CH₃)—; —CH₂CH(CH₃)(C₆H₄)CH(CH₃)CH₂—; —CH₂CH₂CH₂CH₂—,—CH₂CH₂CH(CH₃)—; —CH₂CH(CH₂CH₃)—; —CH₂CH₂CH₂CH(CH₃)—,—CH₂CH₂CH(CH₂CH₃)—; —CH₂CH(CH₂CH₂CH₃)—; —CH₂CH(CH₃)CH₂CH₂—;—CH₂CH(CH₃)CH(CH₃)—; —CH₂C(CH₃)(CH₂CH₃)—; —CH₂CH₂CH(CH₃)CH₂—;—CH₂CH₂C(CH₃)₂—; —CH₂CH[CH(CH₃)₂]—; —CH₂CH₂-norbornyl-,—CH₂CH₂-cyclohexyl-; any of the diradicals obtainable from norbornane,cyclohexane, cyclopentane, tetrahydrodicyclopentadiene, or cyclododeceneby loss of two hydrogen atoms; the structures derivable from limonene,—CH₂CH(4—CH₃—1—C₆H₉—)CH₃; —CH₂CH₂(vinylC₆H₉)CH₂CH₂— and—CH₂CH₂(vinylC₆H₉)CH(CH₃)—; —CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH₂CH₂—;—CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH(CH₃)—; —CH₂C[CH₂CH₂CH═C(CH₃)₂](C₂CH₃)—;—CH₂CH₂CH[CH₂CH₂CH═C(CH₃)₂]CH₂—, —CH₂CH₂(C—)(CH₃)[CH₂CH₂CH═C(CH₃)₂];—CH₂CH[CH(CH₃)[CH₂CH₂CH═C(CH₃)₂]]—; —CH₂CH(CH═CH₂)CH₂CH₂CH₂C(CH₃)₂—,—CH₂CH(CH═CH₂)CH₂CH₂CH[CH(CH₃)₂]—, —CH₂C(═CH—CH₃)CH₂CH₂CH₂C(CH₃)₂—,—CH₂C(═CH—CH₃)CH₂CH₂CH[CH(CH₃)₂]—, —CH₂CH₂C(═CH₂)CH₂CH₂CH₂C(CH₃)₂—,—CH₂CH₂C(═CH₂)CH₂CH₂CH[CH(CH₃)₂]—, —CH₂CH═C(CH₃)₂CH₂CH₂CH₂C(CH₃)₂—, and—CH₂CH═C(CH₃)₂CH₂CH₂CH[CH(CH₃)₂].
 18. The rubber composition of claim 1wherein the rubber component is at least one sulfur vulcanizable rubberselected from the group consisting of conjugated diene homopolymers andcopolymers, copolymers of at least one conjugated diene and aromaticvinyl compound and mixtures thereof.
 19. The rubber composition of claim1 wherein the organofunctional silane is at least one member selectedfrom the group consisting of thioacetic acid 2-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-ethylester; thioacetic acid3-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-propylester; thiobutyric acid3-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-propylester; octanethioic acid3-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-propylester; octanethioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4,4,6-trimethyl-[1,3,2]dioxasilinan-2-yloxy]-1,1-dimethyl-butoxy}-4,4,6-trimethyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;octanetbioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4-methyl-[1,3,2]dioxasilinan-2-yloxy]-butoxy}-4-methyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;undecanethioic acid S-[3-(2-{3-[21,3;;;-(3-mercapto-propyl)-4-methyl-[1,3,2]dioxasilinan-2-yloxy]-butoxy}-4-methyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;heptanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;heptanethioic acidS-[3-(2-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilepan-2-yl)-propyl]ester; thiopropionic acid3-{2-[3-((3-mercapto-propyl)-methyl-{2-methyl-3-[5-methyl-2-(3-propionylsulfanyl-propyl)-[1,3,2]dioxasilinan-2-yloxy]-propoxy}-silanyloxy)-2-methyl-propoxy]-5-methyl-[1,3,2]dioxasilepan-2-yl}-propylester; octanethioic acid3-{2-[3-((3-mercapto-propyl)-methyl-{2-methyl-3-[5-methyl-2-(3-octanoylsulfanyl-propyl)-[1,3,2]dioxasilinan-2-yloxy]-propoxy}-silanyloxy)-2-methyl-propoxy]-5-methyl-[1,3,2]dioxasilepan-2-yl}-propyl ester; octanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-(3-octanoylsulfanyl-propyl)-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester; octanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;octanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[bis-(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-silanyloxy]-2-methyl-propoxy}-(3-mercapto-propyl)-(3-hydroxy-2-methyl-propoxy)-silanyloxy]-2-methyl-propoxy}-(3-hydroxy-2-methyl-propoxy)-silanyl)-propyl]ester;dimethyl -thiocarbamic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;dimethyl -dithiocarbamic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; dimethyl -dithiocarbamic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; thiocarbonic acid O-ethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;trithiocarbonic acid ethyl ester3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2 -methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; trithiocarbonic acid ethyl ester3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; dithiobutyric acid3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; dithiobutyric acid 3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5 -methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; diethyl -dithiocarbamic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; diethyl -dithiocarbamic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; N-methyl -thiobutyrimidic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; N-methyl -thiobutyrimidic acid3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propylester; thiophosphoric acid O,O′-diethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester; thiophosphoric acid O-ethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester O′-propyl ester; dithiophosphoric acid O-ethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]esterO′-propyl ester; trithiophosphoric acid S,S′-diethyl esterS″-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;tetrathiophosphoric acid diethyl ester 3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl ester;tetrathiophosphoric acid diethyl ester3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl ester; tetrathiophosphoric acid ethyl ester3-((3-hydroxy-2-methyl-propoxy)-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl ester propyl ester; methyl-phosphonodithioic acid S-ethyl esterS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;and, dimethyl-phosphinothioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester.
 20. Therubber composition of claim 1 wherein the organofunctional silane is atleast one member selected from the group consisting of octanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[bis-(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-silanyloxy]-2-methyl-propoxy}-(3-mercapto-propyl)-(3-hydroxy-2-methyl-propoxy)-silanyloxy]-2-methyl-propoxy}-(3-hydroxy-2-methyl-propoxy)-silanyl)-propyl]ester;octanethioic acid S-[3-((3-hydroxy-2-methyl-propoxy)-{3-[{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester;octanethioic acid 3-(2-{3-[2-(3-mercapto-propyl)-5-methyl-[1,3,2]dioxasilinan-2-yloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilinan-2-yl)-propylester; octanethioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4,4,6-trimethyl-[1,3,2]dioxasilinan-2-yloxy]-1,1-dimethyl-butoxy}-4,4,6-trimethyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;octanethioic acidS-[3-(2-{3[2-(3-mercapto-propyl)-4-methyl-[1,3,2]dioxasilinan-2-yloxy]-butoxy}-4-methyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester;undecanethioic acidS-[3-(2-{3-[2-(3-mercapto-propyl)-4-methyl-[1,3,2]dioxasilinan-2-yloxy]-butoxy}-4-methyl-[1,3,2]dioxasilinan-2-yl)-propyl]ester; heptanethioic acidS-[3-((3-hydroxy-2-methyl-propoxy)-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-methyl-silanyl)-propyl]ester; heptanethioic acidS-[3-(2-{3-[(3-hydroxy-2-methyl-propoxy)-(3-mercapto-propyl)-methyl-silanyloxy]-2-methyl-propoxy}-5-methyl-[1,3,2]dioxasilepan-2-yl)-propyl]ester;thiopropionic acid3-{2-[3-((3-mercapto-propyl)-methyl-{2-methyl-3-[5-methyl-2-(3-propionylsulfanyl-propyl)-[1,3,2]dioxasilinan-2-yloxy]-propoxy}-silanyloxy)-2-methyl-propoxy]-5-methyl-[1,3,2]dioxasilepan-2-yl}-propyl ester; andoctanethioic acid3-{2-[3-((3-mercapto-propyl)-methyl-{2-methyl-3-[5-methyl-2-(3-octanoylsulfanyl-propyl)-[1,3,2]dioxasilinan-2-yloxy]-propoxy}-silanyloxy)-2-methyl-propoxy]-5-methyl-[1,3,2]dioxasilepan-2-yl}-propyl ester.
 21. An article of which atleast one component is the cured rubber composition of claim
 1. 22. Atire, at least one component of which comprises the cured rubbercomposition obtained from the rubber composition of claim
 1. 23. Thetire of claim 22 wherein rubber component (a) is at least one sulfurvulcanizable rubber selected from the group consisting of conjugateddiene homopolymers and copolymers, copolymers of at least one conjugateddiene and aromatic vinyl compound and mixtures thereof.
 24. A tire, atleast one component of which comprises the cured rubber compositionobtained from the rubber composition of claim
 18. 25. The tire of claim24 wherein rubber component (a) is at least one sulfur vulcanizablerubber selected from the group consisting of conjugated dienehomopolymers and copolymers, copolymers of at least one conjugated dieneand aromatic vinyl compound and mixtures thereof.
 26. A tire, at leastone component of which comprises the cured rubber composition obtainedfrom the rubber composition of claim
 19. 27. The tire of claim 26wherein rubber component (a) is at least one sulfur vulcanizable rubberselected from the group consisting of conjugated diene homopolymers andcopolymers, copolymers of at least one conjugated diene and aromaticvinyl compound and mixtures thereof.
 28. A tire, at least one componentof which comprises the cured rubber composition obtained from the rubbercomposition of claim
 20. 29. The tire of claim 28 wherein rubbercomponent (a) is at least one sulfur vulcanizable rubber selected fromthe group consisting of conjugated diene homopolymers and copolymers,copolymers of at least one conjugated diene and aromatic vinyl compoundand mixtures thereof.
 30. A process for preparing a rubber compositioncomprising adding to a rubber composition reaction-forming mixture aneffective amount of at least one organofunctional silane of claim
 1. 31.The process of claim 30 wherein the rubber composition further comprisesat least one filler.
 32. The process of claim 30 wherein the rubbercomponent is at least one sulfur vulcanizable rubber selected from thegroup consisting of conjugated diene homopolymers and copolymers,copolymers of at least one conjugated diene and aromatic vinyl compoundand mixtures thereof.